/*-------------------------------------------------------------------------
 *
 * datetime.c
 *	  Support functions for date/time types.
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.206 2009/06/01 16:55:11 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <float.h>
#include <limits.h>
#include <math.h>

#include "access/heapam.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/datetime.h"
#include "utils/memutils.h"
#include "utils/tzparser.h"

/*
 * We don't support locale-aware month names or day-of-week names, or non-arabic numbers,
 * and we know the only alpha or numeric chars we can handle are in the ASCII7 set.
 * So we can use these replacements for the standard versions.
 * I think these are faster.
 */
#undef isdigit
#define isdigit(x) ((x) >= '0' && (x) <= '9')
#undef isalpha
#define isalpha(x) (((x) >= 'a' && (x) <= 'z') || ((x) >= 'A' && (x) <= 'Z'))
#undef isalnum
#define isalnum(x) (isalpha(x) || isdigit(x))

static int DecodeNumber(int flen, char *field, bool haveTextMonth,
			 int fmask, int *tmask,
			 struct pg_tm * tm, fsec_t *fsec, bool *is2digits);
static int DecodeNumberField(int len, char *str,
				  int fmask, int *tmask,
				  struct pg_tm * tm, fsec_t *fsec, bool *is2digits);
static int DecodeTime(char *str, int fmask, int range,
		   int *tmask, struct pg_tm * tm, fsec_t *fsec);
static int	DecodeTimezone(char *str, int *tzp);
static const datetkn *datebsearch(const char *key, const datetkn *base, int nel);
static int	DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
					   struct pg_tm * tm);
static int	ValidateDate(int fmask, bool is2digits, bool bc,
						 struct pg_tm * tm);
static void TrimTrailingZeros(char *str);
static void AppendSeconds(char *cp, int sec, fsec_t fsec,
						  int precision, bool fillzeros);
static void AdjustFractSeconds(double frac, struct pg_tm * tm, fsec_t *fsec,
						int scale);
static void AdjustFractDays(double frac, struct pg_tm * tm, fsec_t *fsec,
						int scale);


const int	day_tab[2][13] =
{
	{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0},
	{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0}
};

char	   *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec", NULL};

char	   *days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday", NULL};


/*****************************************************************************
 *	 PRIVATE ROUTINES														 *
 *****************************************************************************/

/*
 * Definitions for squeezing values into "value"
 * We set aside a high bit for a sign, and scale the timezone offsets
 * in minutes by a factor of 15 (so can represent quarter-hour increments).
 */
#define ABS_SIGNBIT		((char) 0200)
#define VALMASK			((char) 0177)
#define POS(n)			(n)
#define NEG(n)			((n)|ABS_SIGNBIT)
#define SIGNEDCHAR(c)	((c)&ABS_SIGNBIT? -((c)&VALMASK): (c))
#define FROMVAL(tp)		(-SIGNEDCHAR((tp)->value) * 15) /* uncompress */
#define TOVAL(tp, v)	((tp)->value = ((v) < 0? NEG((-(v))/15): POS(v)/15))

/*
 * datetktbl holds date/time keywords.
 *
 * Note that this table must be strictly alphabetically ordered to allow an
 * O(ln(N)) search algorithm to be used.
 *
 * The token field is NOT guaranteed to be NULL-terminated.
 *
 * To keep this table reasonably small, we divide the value for TZ and DTZ
 * entries by 15 (so they are on 15 minute boundaries) and truncate the token
 * field at TOKMAXLEN characters.
 * Formerly, we divided by 10 rather than 15 but there are a few time zones
 * which are 30 or 45 minutes away from an even hour, most are on an hour
 * boundary, and none on other boundaries.
 *
 * The static table contains no TZ or DTZ entries, rather those are loaded
 * from configuration files and stored in timezonetktbl, which has the same
 * format as the static datetktbl.
 */
static datetkn *timezonetktbl = NULL;

static int	sztimezonetktbl = 0;

static const datetkn datetktbl[] = {
	/* token, type, value */
	{EARLY, RESERV, DTK_EARLY}, /* "-infinity" reserved for "early time" */
	{DA_D, ADBC, AD},			/* "ad" for years > 0 */
	{"allballs", RESERV, DTK_ZULU},		/* 00:00:00 */
	{"am", AMPM, AM},
	{"apr", MONTH, 4},
	{"april", MONTH, 4},
	{"at", IGNORE_DTF, 0},		/* "at" (throwaway) */
	{"aug", MONTH, 8},
	{"august", MONTH, 8},
	{DB_C, ADBC, BC},			/* "bc" for years <= 0 */
	{DCURRENT, RESERV, DTK_CURRENT},	/* "current" is always now */
	{"d", UNITS, DTK_DAY},		/* "day of month" for ISO input */
	{"dec", MONTH, 12},
	{"december", MONTH, 12},
	{"dow", RESERV, DTK_DOW},	/* day of week */
	{"doy", RESERV, DTK_DOY},	/* day of year */
	{"dst", DTZMOD, 6},
	{EPOCH, RESERV, DTK_EPOCH}, /* "epoch" reserved for system epoch time */
	{"feb", MONTH, 2},
	{"february", MONTH, 2},
	{"fri", DOW, 5},
	{"friday", DOW, 5},
	{"h", UNITS, DTK_HOUR},		/* "hour" */
	{LATE, RESERV, DTK_LATE},	/* "infinity" reserved for "late time" */
	{INVALID, RESERV, DTK_INVALID},		/* "invalid" reserved for bad time */
	{"isodow", RESERV, DTK_ISODOW},		/* ISO day of week, Sunday == 7 */
	{"isoyear", UNITS, DTK_ISOYEAR},	/* year in terms of the ISO week date */
	{"j", UNITS, DTK_JULIAN},
	{"jan", MONTH, 1},
	{"january", MONTH, 1},
	{"jd", UNITS, DTK_JULIAN},
	{"jul", MONTH, 7},
	{"julian", UNITS, DTK_JULIAN},
	{"july", MONTH, 7},
	{"jun", MONTH, 6},
	{"june", MONTH, 6},
	{"m", UNITS, DTK_MONTH},	/* "month" for ISO input */
	{"mar", MONTH, 3},
	{"march", MONTH, 3},
	{"may", MONTH, 5},
	{"mm", UNITS, DTK_MINUTE},	/* "minute" for ISO input */
	{"mon", DOW, 1},
	{"monday", DOW, 1},
	{"nov", MONTH, 11},
	{"november", MONTH, 11},
	{NOW, RESERV, DTK_NOW},		/* current transaction time */
	{"oct", MONTH, 10},
	{"october", MONTH, 10},
	{"on", IGNORE_DTF, 0},		/* "on" (throwaway) */
	{"pm", AMPM, PM},
	{"s", UNITS, DTK_SECOND},	/* "seconds" for ISO input */
	{"sat", DOW, 6},
	{"saturday", DOW, 6},
	{"sep", MONTH, 9},
	{"sept", MONTH, 9},
	{"september", MONTH, 9},
	{"sun", DOW, 0},
	{"sunday", DOW, 0},
	{"t", ISOTIME, DTK_TIME},	/* Filler for ISO time fields */
	{"thu", DOW, 4},
	{"thur", DOW, 4},
	{"thurs", DOW, 4},
	{"thursday", DOW, 4},
	{TODAY, RESERV, DTK_TODAY}, /* midnight */
	{TOMORROW, RESERV, DTK_TOMORROW},	/* tomorrow midnight */
	{"tue", DOW, 2},
	{"tues", DOW, 2},
	{"tuesday", DOW, 2},
	{"undefined", RESERV, DTK_INVALID}, /* pre-v6.1 invalid time */
	{"wed", DOW, 3},
	{"wednesday", DOW, 3},
	{"weds", DOW, 3},
	{"y", UNITS, DTK_YEAR},		/* "year" for ISO input */
	{YESTERDAY, RESERV, DTK_YESTERDAY}	/* yesterday midnight */
};

static int	szdatetktbl = sizeof datetktbl / sizeof datetktbl[0];

static const datetkn deltatktbl[] = {
	/* token, type, value */
	{"@", IGNORE_DTF, 0},		/* postgres relative prefix */
	{DAGO, AGO, 0},				/* "ago" indicates negative time offset */
	{"c", UNITS, DTK_CENTURY},	/* "century" relative */
	{"cent", UNITS, DTK_CENTURY},		/* "century" relative */
	{"centuries", UNITS, DTK_CENTURY},	/* "centuries" relative */
	{DCENTURY, UNITS, DTK_CENTURY},		/* "century" relative */
	{"d", UNITS, DTK_DAY},		/* "day" relative */
	{DDAY, UNITS, DTK_DAY},		/* "day" relative */
	{"days", UNITS, DTK_DAY},	/* "days" relative */
	{"dec", UNITS, DTK_DECADE}, /* "decade" relative */
	{DDECADE, UNITS, DTK_DECADE},		/* "decade" relative */
	{"decades", UNITS, DTK_DECADE},		/* "decades" relative */
	{"decs", UNITS, DTK_DECADE},	/* "decades" relative */
	{"h", UNITS, DTK_HOUR},		/* "hour" relative */
	{DHOUR, UNITS, DTK_HOUR},	/* "hour" relative */
	{"hours", UNITS, DTK_HOUR}, /* "hours" relative */
	{"hr", UNITS, DTK_HOUR},	/* "hour" relative */
	{"hrs", UNITS, DTK_HOUR},	/* "hours" relative */
	{INVALID, RESERV, DTK_INVALID},		/* reserved for invalid time */
	{"m", UNITS, DTK_MINUTE},	/* "minute" relative */
	{"microsecon", UNITS, DTK_MICROSEC},		/* "microsecond" relative */
	{"mil", UNITS, DTK_MILLENNIUM},		/* "millennium" relative */
	{"millennia", UNITS, DTK_MILLENNIUM},		/* "millennia" relative */
	{DMILLENNIUM, UNITS, DTK_MILLENNIUM},		/* "millennium" relative */
	{"millisecon", UNITS, DTK_MILLISEC},		/* relative */
	{"mils", UNITS, DTK_MILLENNIUM},	/* "millennia" relative */
	{"min", UNITS, DTK_MINUTE}, /* "minute" relative */
	{"mins", UNITS, DTK_MINUTE},	/* "minutes" relative */
	{DMINUTE, UNITS, DTK_MINUTE},		/* "minute" relative */
	{"minutes", UNITS, DTK_MINUTE},		/* "minutes" relative */
	{"mon", UNITS, DTK_MONTH},	/* "months" relative */
	{"mons", UNITS, DTK_MONTH}, /* "months" relative */
	{DMONTH, UNITS, DTK_MONTH}, /* "month" relative */
	{"months", UNITS, DTK_MONTH},
	{"ms", UNITS, DTK_MILLISEC},
	{"msec", UNITS, DTK_MILLISEC},
	{DMILLISEC, UNITS, DTK_MILLISEC},
	{"mseconds", UNITS, DTK_MILLISEC},
	{"msecs", UNITS, DTK_MILLISEC},
	{"qtr", UNITS, DTK_QUARTER},	/* "quarter" relative */
	{DQUARTER, UNITS, DTK_QUARTER},		/* "quarter" relative */
	{"s", UNITS, DTK_SECOND},
	{"sec", UNITS, DTK_SECOND},
	{DSECOND, UNITS, DTK_SECOND},
	{"seconds", UNITS, DTK_SECOND},
	{"secs", UNITS, DTK_SECOND},
	{DTIMEZONE, UNITS, DTK_TZ}, /* "timezone" time offset */
	{"timezone_h", UNITS, DTK_TZ_HOUR}, /* timezone hour units */
	{"timezone_m", UNITS, DTK_TZ_MINUTE},		/* timezone minutes units */
	{"undefined", RESERV, DTK_INVALID}, /* pre-v6.1 invalid time */
	{"us", UNITS, DTK_MICROSEC},	/* "microsecond" relative */
	{"usec", UNITS, DTK_MICROSEC},		/* "microsecond" relative */
	{DMICROSEC, UNITS, DTK_MICROSEC},	/* "microsecond" relative */
	{"useconds", UNITS, DTK_MICROSEC},	/* "microseconds" relative */
	{"usecs", UNITS, DTK_MICROSEC},		/* "microseconds" relative */
	{"w", UNITS, DTK_WEEK},		/* "week" relative */
	{DWEEK, UNITS, DTK_WEEK},	/* "week" relative */
	{"weeks", UNITS, DTK_WEEK}, /* "weeks" relative */
	{"y", UNITS, DTK_YEAR},		/* "year" relative */
	{DYEAR, UNITS, DTK_YEAR},	/* "year" relative */
	{"years", UNITS, DTK_YEAR}, /* "years" relative */
	{"yr", UNITS, DTK_YEAR},	/* "year" relative */
	{"yrs", UNITS, DTK_YEAR}	/* "years" relative */
};

static int	szdeltatktbl = sizeof deltatktbl / sizeof deltatktbl[0];

static const datetkn *datecache[MAXDATEFIELDS] = {NULL};

static const datetkn *deltacache[MAXDATEFIELDS] = {NULL};


/*
 * strtoi --- just like strtol, but returns int not long
 */

static inline int strtoi(const char *nptr, char **endptr, __attribute__((unused)) int base)
{
	/* Assume base = 10 */
	/* Assume number will not be larger than int32 */
	/* Assume number isn't hex with 0x prefix */
	/* Assume leading whitespace can only be an ASCII space */
	/* Ignores `locale' stuff.  Assumes that the upper and lower case alphabets and digits are each contiguous. */
	const char *s = nptr;
	unsigned long acc;
	unsigned char c;

	int			neg = 0,
				any;

	if (*s != ' ' && isspace(*s))
		Assert("bug ");
	/*
	 * Skip white space and pick up leading +/- sign if any.
	 * Do we need this for DATE?
	 */
	do
	{
		c = *s++;
	} while (c == ' ');
	if (c == '-')
	{
		neg = 1;
		c = *s++;
	}
	else if (c == '+')
		c = *s++;

	for (acc = 0, any = 0;; c = *s++)
	{
		if (c >= '0' && c <= '9')
			c -= '0';
		else
			break;
		any = 1;
		acc *= 10;
		acc += c;
	}

	if (acc > 2147483647)
		errno = ERANGE;

	if (neg)
		acc = -acc;

	if (endptr != 0)
		*endptr = any ? (char *)(s - 1) : (char *) nptr;
		
	return acc;
}

/*
 * Calendar time to Julian date conversions.
 * Julian date is commonly used in astronomical applications,
 *	since it is numerically accurate and computationally simple.
 * The algorithms here will accurately convert between Julian day
 *	and calendar date for all non-negative Julian days
 *	(i.e. from Nov 24, -4713 on).
 *
 * These routines will be used by other date/time packages
 * - thomas 97/02/25
 *
 * Rewritten to eliminate overflow problems. This now allows the
 * routines to work correctly for all Julian day counts from
 * 0 to 2147483647	(Nov 24, -4713 to Jun 3, 5874898) assuming
 * a 32-bit integer. Longer types should also work to the limits
 * of their precision.
 */

int
date2j(int y, int m, int d)
{
	int			julian;
	int			century;

	if (m > 2)
	{
		m += 1;
		y += 4800;
	}
	else
	{
		m += 13;
		y += 4799;
	}

	century = y / 100;
	julian = y * 365 - 32167;
	julian += y / 4 - century + century / 4;
	julian += 7834 * m / 256 + d;

	return julian;
}	/* date2j() */

void
j2date(int jd, int *year, int *month, int *day)
{
	unsigned int julian;
	unsigned int quad;
	unsigned int extra;
	int			y;

	julian = jd;
	julian += 32044;
	quad = julian / 146097;
	extra = (julian - quad * 146097) * 4 + 3;
	julian += 60 + quad * 3 + extra / 146097;
	quad = julian / 1461;
	julian -= quad * 1461;
	y = julian * 4 / 1461;
	julian = ((y != 0) ? ((julian + 305) % 365) : ((julian + 306) % 366))
		+ 123;
	y += quad * 4;
	*year = y - 4800;
	quad = julian * 2141 / 65536;
	*day = julian - 7834 * quad / 256;
	*month = (quad + 10) % 12 + 1;

	return;
}	/* j2date() */


/*
 * j2day - convert Julian date to day-of-week (0..6 == Sun..Sat)
 *
 * Note: various places use the locution j2day(date - 1) to produce a
 * result according to the convention 0..6 = Mon..Sun.	This is a bit of
 * a crock, but will work as long as the computation here is just a modulo.
 */
int
j2day(int date)
{
	unsigned int day;

	day = date;

	day += 1;
	day %= 7;

	return (int) day;
}	/* j2day() */


/*
 * GetCurrentDateTime()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm.
 */
void
GetCurrentDateTime(struct pg_tm * tm)
{
	int			tz;
	fsec_t		fsec;

	timestamp2tm(GetCurrentTransactionStartTimestamp(), &tz, tm, &fsec,
				 NULL, NULL);
	/* Note: don't pass NULL tzp to timestamp2tm; affects behavior */
}

/*
 * GetCurrentTimeUsec()
 *
 * Get the transaction start time ("now()") broken down as a struct pg_tm,
 * including fractional seconds and timezone offset.
 */
void
GetCurrentTimeUsec(struct pg_tm * tm, fsec_t *fsec, int *tzp)
{
	int			tz;

	timestamp2tm(GetCurrentTransactionStartTimestamp(), &tz, tm, fsec,
				 NULL, NULL);
	/* Note: don't pass NULL tzp to timestamp2tm; affects behavior */
	if (tzp != NULL)
		*tzp = tz;
}


/* TrimTrailingZeros()
 * ... resulting from printing numbers with full precision.
 *
 * Before Postgres 8.4, this always left at least 2 fractional digits,
 * but conversations on the lists suggest this isn't desired
 * since showing '0.10' is misleading with values of precision(1).
 */
static void
TrimTrailingZeros(char *str)
{
	int			len = strlen(str);

	while (len > 1 && *(str + len - 1) == '0' && *(str + len - 2) != '.')
	{
		len--;
		*(str + len) = '\0';
	}
}

/*
 * Append sections and fractional seconds (if any) at *cp.
 * precision is the max number of fraction digits, fillzeros says to
 * pad to two integral-seconds digits.
 * Note that any sign is stripped from the input seconds values.
 */
static void
AppendSeconds(char *cp, int sec, fsec_t fsec, int precision, bool fillzeros)
{
	int j = 0;
	/*
	 * Print fractional seconds if any.  The field widths here should
	 * be at least equal to MAX_TIMESTAMP_PRECISION.
	 *
	 * In float mode, don't print fractional seconds before 1 AD,
	 * since it's unlikely there's any precision left ...
	 */
	if (fsec ==  0)
	{
		if (fillzeros || abs(sec)  > 9)
					cp[j++] = abs(sec)  / 10 + '0';
		cp[j++] =abs(sec)  % 10 + '0';
		cp[j] = '\0';
	}
	else
	{
#ifdef HAVE_INT64_TIMESTAMP

		if (fillzeros || abs(sec)  > 9)
			cp[j++] = abs(sec)  / 10 + '0';
		cp[j++] = abs(sec)  % 10 + '0';
		cp[j++] = '.';
		cp[j++] =  ((int) Abs(fsec) )/ 100000 + '0';
		cp[j++] = ((int) Abs(fsec) ) / 10000 % 10 + '0';
		cp[j++] = ((int) Abs(fsec) ) / 1000 % 10 + '0';
		cp[j++] = ((int) Abs(fsec) ) / 100 % 10 + '0';
		cp[j++] = ((int) Abs(fsec) ) / 10 % 10 + '0';
		cp[j++] = ((int) Abs(fsec) ) % 10 + '0';
		cp[j] = '\0';

#else
		if (fillzeros)
			sprintf(cp, "%0*.*f", precision + 3, precision, fabs(sec + fsec));
		else
			sprintf(cp, "%.*f", precision, fabs(sec + fsec));
#endif 
		TrimTrailingZeros(cp);
	}
}

/* Variant of above that's specialized to timestamp case */
static void
AppendTimestampSeconds(char *cp, struct pg_tm * tm, fsec_t fsec)
{
	/*
	 * In float mode, don't print fractional seconds before 1 AD, since it's
	 * unlikely there's any precision left ...
	 */
#ifndef HAVE_INT64_TIMESTAMP
	if (tm->tm_year <= 0)
		fsec = 0;
#endif
	AppendSeconds(cp, tm->tm_sec, fsec, MAX_TIMESTAMP_PRECISION, true);
}

/*
 * Multiply frac by scale (to produce seconds) and add to *tm & *fsec.
 * We assume the input frac is less than 1 so overflow is not an issue.
 */
static void
AdjustFractSeconds(double frac, struct pg_tm * tm, fsec_t *fsec, int scale)
{
	int	sec;

	if (frac == 0)
		return;
	frac       *= scale;
	sec         = (int) frac;
	tm->tm_sec += sec;
	frac       -= sec;
#ifdef HAVE_INT64_TIMESTAMP
	*fsec      += rint(frac * 1000000);
#else
	*fsec      += frac;
#endif
}

/* As above, but initial scale produces days */
static void
AdjustFractDays(double frac, struct pg_tm * tm, fsec_t *fsec, int scale)
{
	int	extra_days;

	if (frac == 0)
		return;
	frac        *= scale;
	extra_days   = (int) frac;
	tm->tm_mday += extra_days;
	frac        -= extra_days;
	AdjustFractSeconds(frac, tm, fsec, SECS_PER_DAY);
}

/* Fetch a fractional-second value with suitable error checking */
static int
ParseFractionalSecond(char *cp, fsec_t *fsec)
{
	double		frac;

	/* Caller should always pass the start of the fraction part */
	Assert(*cp == '.');
	errno = 0;
	frac = strtod(cp, &cp);
	/* check for parse failure */
	if (*cp != '\0' || errno != 0)
		return DTERR_BAD_FORMAT;
#ifdef HAVE_INT64_TIMESTAMP
	*fsec = rint(frac * 1000000);
#else
	*fsec = frac;
#endif
	return 0;
}


/* ParseDateTime()
 *	Break string into tokens based on a date/time context.
 *	Returns 0 if successful, DTERR code if bogus input detected.
 *
 * timestr - the input string
 * workbuf - workspace for field string storage. This must be
 *	 larger than the largest legal input for this datetime type --
 *	 some additional space will be needed to NUL terminate fields.
 * buflen - the size of workbuf
 * field[] - pointers to field strings are returned in this array
 * ftype[] - field type indicators are returned in this array
 * maxfields - dimensions of the above two arrays
 * *numfields - set to the actual number of fields detected
 *
 * The fields extracted from the input are stored as separate,
 * null-terminated strings in the workspace at workbuf. Any text is
 * converted to lower case.
 *
 * Several field types are assigned:
 *	DTK_NUMBER - digits and (possibly) a decimal point
 *	DTK_DATE - digits and two delimiters, or digits and text
 *	DTK_TIME - digits, colon delimiters, and possibly a decimal point
 *	DTK_STRING - text (no digits or punctuation)
 *	DTK_SPECIAL - leading "+" or "-" followed by text
 *	DTK_TZ - leading "+" or "-" followed by digits (also eats ':', '.', '-')
 *
 * Note that some field types can hold unexpected items:
 *	DTK_NUMBER can hold date fields (yy.ddd)
 *	DTK_STRING can hold months (January) and time zones (PST)
 *	DTK_DATE can hold time zone names (America/New_York, GMT-8)
 */
int
ParseDateTime(const char *timestr, char *workbuf, size_t buflen,
			  char **field, int *ftype, int maxfields, int *numfields)
{
	int			nf = 0;
	const char *cp = timestr;
	char	   *bufp = workbuf;
	const char *bufend = workbuf + buflen;

	/*
	 * Set the character pointed-to by "bufptr" to "newchar", and increment
	 * "bufptr". "end" gives the end of the buffer -- we return an error if
	 * there is no space left to append a character to the buffer. Note that
	 * "bufptr" is evaluated twice.
	 */
#define APPEND_CHAR(bufptr, end, newchar)		\
	do											\
	{											\
		if (((bufptr) + 1) >= (end))			\
			return DTERR_BAD_FORMAT;			\
		*(bufptr)++ = newchar;					\
	} while (0)

	/* outer loop through fields */
	while (*cp != '\0')
	{
		/* Ignore spaces between fields */
		if (isspace((unsigned char) *cp))
		{
			cp++;
			continue;
		}

		/* Record start of current field */
		if (nf >= maxfields)
			return DTERR_BAD_FORMAT;
		field[nf] = bufp;

		/* leading digit? then date or time */
		if (isdigit((unsigned char) *cp))
		{
			APPEND_CHAR(bufp, bufend, *cp++);
			while (isdigit((unsigned char) *cp))
				APPEND_CHAR(bufp, bufend, *cp++);

			/* time field? */
			if (*cp == ':')
			{
				ftype[nf] = DTK_TIME;
				APPEND_CHAR(bufp, bufend, *cp++);
				while (isdigit((unsigned char) *cp) ||
					   (*cp == ':') || (*cp == '.'))
					APPEND_CHAR(bufp, bufend, *cp++);
			}
			/* date field? allow embedded text month */
			else if (*cp == '-' || *cp == '/' || *cp == '.')
			{
				/* save delimiting character to use later */
				char		delim = *cp;

				APPEND_CHAR(bufp, bufend, *cp++);
				/* second field is all digits? then no embedded text month */
				if (isdigit((unsigned char) *cp))
				{
					ftype[nf] = ((delim == '.') ? DTK_NUMBER : DTK_DATE);
					while (isdigit((unsigned char) *cp))
						APPEND_CHAR(bufp, bufend, *cp++);

					/*
					 * insist that the delimiters match to get a three-field
					 * date.
					 */
					if (*cp == delim)
					{
						ftype[nf] = DTK_DATE;
						APPEND_CHAR(bufp, bufend, *cp++);
						while (isdigit((unsigned char) *cp) || *cp == delim)
							APPEND_CHAR(bufp, bufend, *cp++);
					}
				}
				else
				{
					ftype[nf] = DTK_DATE;
					while (isalnum((unsigned char) *cp) || *cp == delim)
						APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
				}
			}

			/*
			 * otherwise, number only and will determine year, month, day, or
			 * concatenated fields later...
			 */
			else
				ftype[nf] = DTK_NUMBER;
		}
		/* Leading decimal point? Then fractional seconds... */
		else if (*cp == '.')
		{
			APPEND_CHAR(bufp, bufend, *cp++);
			while (isdigit((unsigned char) *cp))
				APPEND_CHAR(bufp, bufend, *cp++);

			ftype[nf] = DTK_NUMBER;
		}

		/*
		 * text? then date string, month, day of week, special, or timezone
		 */
		else if (isalpha((unsigned char) *cp))
		{
			bool	is_date;

			ftype[nf] = DTK_STRING;
			APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
			while (isalpha((unsigned char) *cp))
				APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));

			/*
			 * Dates can have embedded '-', '/', or '.' separators.  It could
			 * also be a timezone name containing embedded '/', '+', '-', '_',
			 * or ':' (but '_' or ':' can't be the first punctuation). If the
			 * next character is a digit or '+', we need to check whether what
			 * we have so far is a recognized non-timezone keyword --- if so,
			 * don't believe that this is the start of a timezone.
			 */
			is_date = false;
			if (*cp == '-' || *cp == '/' || *cp == '.')
				is_date = true;
			else if (*cp == '+' || isdigit((unsigned char) *cp))
			{
				*bufp = '\0';	/* null-terminate current field value */
				/* we need search only the core token table, not TZ names */
				if (datebsearch(field[nf], datetktbl, szdatetktbl) == NULL)
					is_date = true;
			}
			if (is_date)
			{
				ftype[nf] = DTK_DATE;
				do
				{
					APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
				} while (*cp == '+' || *cp == '-' ||
						 *cp == '/' || *cp == '_' ||
						 *cp == '.' || *cp == ':' ||
						 isalnum((unsigned char) *cp));
			}
		}
		/* sign? then special or numeric timezone */
		else if (*cp == '+' || *cp == '-')
		{
			APPEND_CHAR(bufp, bufend, *cp++);
			/* soak up leading whitespace */
			while (isspace((unsigned char) *cp))
				cp++;
			/* numeric timezone? */
			/* note that "DTK_TZ" could also be a signed float or yyyy-mm */
			if (isdigit((unsigned char) *cp))
			{
				ftype[nf] = DTK_TZ;
				APPEND_CHAR(bufp, bufend, *cp++);
				while (isdigit((unsigned char) *cp) ||
					   *cp == ':' || *cp == '.' || *cp == '-')
					APPEND_CHAR(bufp, bufend, *cp++);
			}
			/* special? */
			else if (isalpha((unsigned char) *cp))
			{
				ftype[nf] = DTK_SPECIAL;
				APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
				while (isalpha((unsigned char) *cp))
					APPEND_CHAR(bufp, bufend, pg_tolower((unsigned char) *cp++));
			}
			/* otherwise something wrong... */
			else
				return DTERR_BAD_FORMAT;
		}
		/* ignore other punctuation but use as delimiter */
		else if (ispunct((unsigned char) *cp))
		{
			cp++;
			continue;
		}
		/* otherwise, something is not right... */
		else
			return DTERR_BAD_FORMAT;

		/* force in a delimiter after each field */
		*bufp++ = '\0';
		nf++;
	}

	*numfields = nf;

	return 0;
}


/* DecodeDateTime()
 * Interpret previously parsed fields for general date and time.
 * Return 0 if full date, 1 if only time, and negative DTERR code if problems.
 * (Currently, all callers treat 1 as an error return too.)
 *
 *		External format(s):
 *				"<weekday> <month>-<day>-<year> <hour>:<minute>:<second>"
 *				"Fri Feb-7-1997 15:23:27"
 *				"Feb-7-1997 15:23:27"
 *				"2-7-1997 15:23:27"
 *				"1997-2-7 15:23:27"
 *				"1997.038 15:23:27"		(day of year 1-366)
 *		Also supports input in compact time:
 *				"970207 152327"
 *				"97038 152327"
 *				"20011225T040506.789-07"
 *
 * Use the system-provided functions to get the current time zone
 *	if not specified in the input string.
 *
 * If the date is outside the range of pg_time_t (in practice that could only
 * happen if pg_time_t is just 32 bits), then assume UTC time zone - thomas
 * 1997-05-27
 */
int
DecodeDateTime(char **field, int *ftype, int nf,
			   int *dtype, struct pg_tm * tm, fsec_t *fsec, int *tzp)
{
	int			fmask = 0,
				tmask,
				type;
	int			ptype = 0;		/* "prefix type" for ISO y2001m02d04 format */
	int			i;
	int			val;
	int			dterr;
	int			mer = HR24;
	bool		haveTextMonth = FALSE;
	bool		is2digits = FALSE;
	bool		bc = FALSE;
	pg_tz	   *namedTz = NULL;

	/*
	 * We'll insist on at least all of the date fields, but initialize the
	 * remaining fields in case they are not set later...
	 */
	*dtype = DTK_DATE;
	tm->tm_hour = 0;
	tm->tm_min = 0;
	tm->tm_sec = 0;
	*fsec = 0;
	/* don't know daylight savings time status apriori */
	tm->tm_isdst = -1;
	if (tzp != NULL)
		*tzp = 0;

	for (i = 0; i < nf; i++)
	{
		switch (ftype[i])
		{
			case DTK_DATE:
				/***
				 * Integral julian day with attached time zone?
				 * All other forms with JD will be separated into
				 * distinct fields, so we handle just this case here.
				 ***/
				if (ptype == DTK_JULIAN)
				{
					char	   *cp;
					int			val;

					if (tzp == NULL)
						return DTERR_BAD_FORMAT;

					errno = 0;
					val = strtoi(field[i], &cp, 10);
					if (errno == ERANGE)
						return DTERR_FIELD_OVERFLOW;

					j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
					/* Get the time zone from the end of the string */
					dterr = DecodeTimezone(cp, tzp);
					if (dterr)
						return dterr;

					tmask = DTK_DATE_M | DTK_TIME_M | DTK_M(TZ);
					ptype = 0;
					break;
				}
				/***
				 * Already have a date? Then this might be a time zone name
				 * with embedded punctuation (e.g. "America/New_York") or a
				 * run-together time with trailing time zone (e.g. hhmmss-zz).
				 * - thomas 2001-12-25
				 *
				 * We consider it a time zone if we already have month & day.
				 * This is to allow the form "mmm dd hhmmss tz year", which
				 * we've historically accepted.
				 ***/
				else if (ptype != 0 ||
						 ((fmask & (DTK_M(MONTH) | DTK_M(DAY))) ==
						  (DTK_M(MONTH) | DTK_M(DAY))))
				{
					/* No time zone accepted? Then quit... */
					if (tzp == NULL)
						return DTERR_BAD_FORMAT;

					if (isdigit((unsigned char) *field[i]) || ptype != 0)
					{
						char	   *cp;

						if (ptype != 0)
						{
							/* Sanity check; should not fail this test */
							if (ptype != DTK_TIME)
								return DTERR_BAD_FORMAT;
							ptype = 0;
						}

						/*
						 * Starts with a digit but we already have a time
						 * field? Then we are in trouble with a date and time
						 * already...
						 */
						if ((fmask & DTK_TIME_M) == DTK_TIME_M)
							return DTERR_BAD_FORMAT;

						if ((cp = strchr(field[i], '-')) == NULL)
							return DTERR_BAD_FORMAT;

						/* Get the time zone from the end of the string */
						dterr = DecodeTimezone(cp, tzp);
						if (dterr)
							return dterr;
						*cp = '\0';

						/*
						 * Then read the rest of the field as a concatenated
						 * time
						 */
						dterr = DecodeNumberField(strlen(field[i]), field[i],
												  fmask,
												  &tmask, tm,
												  fsec, &is2digits);
						if (dterr < 0)
							return dterr;

						/*
						 * modify tmask after returning from
						 * DecodeNumberField()
						 */
						tmask |= DTK_M(TZ);
					}
					else
					{
						namedTz = pg_tzset(field[i]);
						if (!namedTz)
						{
							/*
							 * We should return an error code instead of
							 * ereport'ing directly, but then there is no way
							 * to report the bad time zone name.
							 */
							ereport(ERROR,
									(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
									 errmsg("time zone \"%s\" not recognized",
											field[i]),
													 errOmitLocation(true)));
						}
						/* we'll apply the zone setting below */
						tmask = DTK_M(TZ);
					}
				}
				else
				{
					dterr = DecodeDate(field[i], fmask,
									   &tmask, &is2digits, tm);
					if (dterr)
						return dterr;
				}
				break;

			case DTK_TIME:
				dterr = DecodeTime(field[i], fmask, INTERVAL_FULL_RANGE,
								   &tmask, tm, fsec);
				if (dterr)
					return dterr;

				/*
				 * Check upper limit on hours; other limits checked in
				 * DecodeTime()
				 */
				/* test for > 24:00:00 */
				if (tm->tm_hour > 24 ||
					(tm->tm_hour == 24 &&
					 (tm->tm_min > 0 || tm->tm_sec > 0 || *fsec > 0)))
					return DTERR_FIELD_OVERFLOW;
				break;

			case DTK_TZ:
				{
					int			tz;

					if (tzp == NULL)
						return DTERR_BAD_FORMAT;

					dterr = DecodeTimezone(field[i], &tz);
					if (dterr)
						return dterr;
					*tzp = tz;
					tmask = DTK_M(TZ);
				}
				break;

			case DTK_NUMBER:

				/*
				 * Was this an "ISO date" with embedded field labels? An
				 * example is "y2001m02d04" - thomas 2001-02-04
				 */
				if (ptype != 0)
				{
					char	   *cp;
					int			val;

					errno = 0;
					val = strtoi(field[i], &cp, 10);
					if (errno == ERANGE)
						return DTERR_FIELD_OVERFLOW;

					/*
					 * only a few kinds are allowed to have an embedded
					 * decimal
					 */
					if (*cp == '.')
						switch (ptype)
						{
							case DTK_JULIAN:
							case DTK_TIME:
							case DTK_SECOND:
								break;
							default:
								return DTERR_BAD_FORMAT;
								break;
						}
					else if (*cp != '\0')
						return DTERR_BAD_FORMAT;

					switch (ptype)
					{
						case DTK_YEAR:
							tm->tm_year = val;
							tmask = DTK_M(YEAR);
							break;

						case DTK_MONTH:

							/*
							 * already have a month and hour? then assume
							 * minutes
							 */
							if ((fmask & DTK_M(MONTH)) != 0 &&
								(fmask & DTK_M(HOUR)) != 0)
							{
								tm->tm_min = val;
								tmask = DTK_M(MINUTE);
							}
							else
							{
								tm->tm_mon = val;
								tmask = DTK_M(MONTH);
							}
							break;

						case DTK_DAY:
							tm->tm_mday = val;
							tmask = DTK_M(DAY);
							break;

						case DTK_HOUR:
							tm->tm_hour = val;
							tmask = DTK_M(HOUR);
							break;

						case DTK_MINUTE:
							tm->tm_min = val;
							tmask = DTK_M(MINUTE);
							break;

						case DTK_SECOND:
							tm->tm_sec = val;
							tmask = DTK_M(SECOND);
							if (*cp == '.')
							{
								dterr = ParseFractionalSecond(cp, fsec);
								if (dterr)
									return dterr;
								tmask = DTK_ALL_SECS_M;
							}
							break;

						case DTK_TZ:
							tmask = DTK_M(TZ);
							dterr = DecodeTimezone(field[i], tzp);
							if (dterr)
								return dterr;
							break;

						case DTK_JULIAN:
							/***
							 * previous field was a label for "julian date"?
							 ***/
							tmask = DTK_DATE_M;
							j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
							/* fractional Julian Day? */
							if (*cp == '.')
							{
								double		time;

								errno = 0;
								time = strtod(cp, &cp);
								if (*cp != '\0' || errno != 0)
									return DTERR_BAD_FORMAT;

#ifdef HAVE_INT64_TIMESTAMP
								time *= USECS_PER_DAY;
#else
								time *= SECS_PER_DAY;
#endif
								dt2time(time,
										&tm->tm_hour, &tm->tm_min,
										&tm->tm_sec, fsec);
								tmask |= DTK_TIME_M;
							}
							break;

						case DTK_TIME:
							/* previous field was "t" for ISO time */
							dterr = DecodeNumberField(strlen(field[i]), field[i],
													  (fmask | DTK_DATE_M),
													  &tmask, tm,
													  fsec, &is2digits);
							if (dterr < 0)
								return dterr;
							if (tmask != DTK_TIME_M)
								return DTERR_BAD_FORMAT;
							break;

						default:
							return DTERR_BAD_FORMAT;
							break;
					}

					ptype = 0;
					*dtype = DTK_DATE;
				}
				else
				{
					char	   *cp;
					int			flen;

					flen = strlen(field[i]);
					cp = strchr(field[i], '.');

					/* 
					 * Embedded decimal and no date yet? Only do this if
					 * we're not looking at something like YYYYMMDDHHMMSS.mm
					 */
					if (cp != NULL && !(fmask & DTK_DATE_M) && flen <= 14)
					{
						dterr = DecodeDate(field[i], fmask,
										   &tmask, &is2digits, tm);
						if (dterr)
							return dterr;
					}
					/* embedded decimal and several digits before? */
					else if (cp != NULL && flen - strlen(cp) > 2)
					{
						/*
						 * Interpret as a concatenated date or time Set the
						 * type field to allow decoding other fields later.
						 * Example: 20011223 or 040506
						 */
						dterr = DecodeNumberField(flen, field[i], fmask,
												  &tmask, tm,
												  fsec, &is2digits);
						if (dterr < 0)
							return dterr;
					}
					else if (flen > 4)
					{
						dterr = DecodeNumberField(flen, field[i], fmask,
												  &tmask, tm,
												  fsec, &is2digits);
						if (dterr < 0)
							return dterr;
					}
					/* otherwise it is a single date/time field... */
					else
					{
						dterr = DecodeNumber(flen, field[i],
											 haveTextMonth, fmask,
											 &tmask, tm,
											 fsec, &is2digits);
						if (dterr)
							return dterr;
					}
				}
				break;

			case DTK_STRING:
			case DTK_SPECIAL:
				type = DecodeSpecial(i, field[i], &val);
				if (type == IGNORE_DTF)
					continue;

				tmask = DTK_M(type);
				switch (type)
				{
					case RESERV:
						switch (val)
						{
							case DTK_CURRENT:
								ereport(ERROR,
									 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
									  errmsg("date/time value \"current\" is no longer supported"),
									  errOmitLocation(true)));

								return DTERR_BAD_FORMAT;
								break;

							case DTK_NOW:
								tmask = (DTK_DATE_M | DTK_TIME_M | DTK_M(TZ));
								*dtype = DTK_DATE;
								GetCurrentTimeUsec(tm, fsec, tzp);
								break;

							case DTK_YESTERDAY:
								tmask = DTK_DATE_M;
								*dtype = DTK_DATE;
								GetCurrentDateTime(tm);
								j2date(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - 1,
									&tm->tm_year, &tm->tm_mon, &tm->tm_mday);
								tm->tm_hour = 0;
								tm->tm_min = 0;
								tm->tm_sec = 0;
								break;

							case DTK_TODAY:
								tmask = DTK_DATE_M;
								*dtype = DTK_DATE;
								GetCurrentDateTime(tm);
								tm->tm_hour = 0;
								tm->tm_min = 0;
								tm->tm_sec = 0;
								break;

							case DTK_TOMORROW:
								tmask = DTK_DATE_M;
								*dtype = DTK_DATE;
								GetCurrentDateTime(tm);
								j2date(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + 1,
									&tm->tm_year, &tm->tm_mon, &tm->tm_mday);
								tm->tm_hour = 0;
								tm->tm_min = 0;
								tm->tm_sec = 0;
								break;

							case DTK_ZULU:
								tmask = (DTK_TIME_M | DTK_M(TZ));
								*dtype = DTK_DATE;
								tm->tm_hour = 0;
								tm->tm_min = 0;
								tm->tm_sec = 0;
								if (tzp != NULL)
									*tzp = 0;
								break;

							default:
								*dtype = val;
						}

						break;

					case MONTH:

						/*
						 * already have a (numeric) month? then see if we can
						 * substitute...
						 */
						if ((fmask & DTK_M(MONTH)) && !haveTextMonth &&
							!(fmask & DTK_M(DAY)) && tm->tm_mon >= 1 &&
							tm->tm_mon <= 31)
						{
							tm->tm_mday = tm->tm_mon;
							tmask = DTK_M(DAY);
						}
						haveTextMonth = TRUE;
						tm->tm_mon = val;
						break;

					case DTZMOD:

						/*
						 * daylight savings time modifier (solves "MET DST"
						 * syntax)
						 */
						tmask |= DTK_M(DTZ);
						tm->tm_isdst = 1;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp += val * MINS_PER_HOUR;
						break;

					case DTZ:

						/*
						 * set mask for TZ here _or_ check for DTZ later when
						 * getting default timezone
						 */
						tmask |= DTK_M(TZ);
						tm->tm_isdst = 1;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp = val * MINS_PER_HOUR;
						break;

					case TZ:
						tm->tm_isdst = 0;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp = val * MINS_PER_HOUR;
						break;

					case IGNORE_DTF:
						break;

					case AMPM:
						mer = val;
						break;

					case ADBC:
						bc = (val == BC);
						break;

					case DOW:
						tm->tm_wday = val;
						break;

					case UNITS:
						tmask = 0;
						ptype = val;
						break;

					case ISOTIME:

						/*
						 * This is a filler field "t" indicating that the next
						 * field is time. Try to verify that this is sensible.
						 */
						tmask = 0;

						/* No preceding date? Then quit... */
						if ((fmask & DTK_DATE_M) != DTK_DATE_M)
							return DTERR_BAD_FORMAT;

						/***
						 * We will need one of the following fields:
						 *	DTK_NUMBER should be hhmmss.fff
						 *	DTK_TIME should be hh:mm:ss.fff
						 *	DTK_DATE should be hhmmss-zz
						 ***/
						if (i >= nf - 1 ||
							(ftype[i + 1] != DTK_NUMBER &&
							 ftype[i + 1] != DTK_TIME &&
							 ftype[i + 1] != DTK_DATE))
							return DTERR_BAD_FORMAT;

						ptype = val;
						break;

					case UNKNOWN_FIELD:

						/*
						 * Before giving up and declaring error, check to see
						 * if it is an all-alpha timezone name.
						 */
						namedTz = pg_tzset(field[i]);
						if (!namedTz)
							return DTERR_BAD_FORMAT;
						/* we'll apply the zone setting below */
						tmask = DTK_M(TZ);
						break;

					default:
						return DTERR_BAD_FORMAT;
				}
				break;

			default:
				return DTERR_BAD_FORMAT;
		}

		if (tmask & fmask)
			return DTERR_BAD_FORMAT;
		fmask |= tmask;
	}				/* end loop over fields */

	/* do final checking/adjustment of Y/M/D fields */
	dterr = ValidateDate(fmask, is2digits, bc, tm);
	if (dterr)
		return dterr;

	/* handle AM/PM */
	if (mer != HR24 && tm->tm_hour > 12)
		return DTERR_FIELD_OVERFLOW;
	if (mer == AM && tm->tm_hour == 12)
		tm->tm_hour = 0;
	else if (mer == PM && tm->tm_hour != 12)
		tm->tm_hour += 12;

	/* do additional checking for full date specs... */
	if (*dtype == DTK_DATE)
	{
		if ((fmask & DTK_DATE_M) != DTK_DATE_M)
		{
			if ((fmask & DTK_TIME_M) == DTK_TIME_M)
				return 1;
			return DTERR_BAD_FORMAT;
		}

		/*
		 * If we had a full timezone spec, compute the offset (we could not do
		 * it before, because we need the date to resolve DST status).
		 */
		if (namedTz != NULL)
		{
			/* daylight savings time modifier disallowed with full TZ */
			if (fmask & DTK_M(DTZMOD))
				return DTERR_BAD_FORMAT;

			*tzp = DetermineTimeZoneOffset(tm, namedTz);
		}

		/* timezone not specified? then find local timezone if possible */
		if (tzp != NULL && !(fmask & DTK_M(TZ)))
		{
			/*
			 * daylight savings time modifier but no standard timezone? then
			 * error
			 */
			if (fmask & DTK_M(DTZMOD))
				return DTERR_BAD_FORMAT;

			*tzp = DetermineTimeZoneOffset(tm, session_timezone);
		}
	}

	return 0;
}


/* DetermineTimeZoneOffset()
 *
 * Given a struct pg_tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min, and
 * tm_sec fields are set, attempt to determine the applicable time zone
 * (ie, regular or daylight-savings time) at that time.  Set the struct pg_tm's
 * tm_isdst field accordingly, and return the actual timezone offset.
 *
 * Note: it might seem that we should use mktime() for this, but bitter
 * experience teaches otherwise.  This code is much faster than most versions
 * of mktime(), anyway.
 */
int
DetermineTimeZoneOffset(struct pg_tm * tm, pg_tz *tzp)
{
	int			date,
				sec;
	pg_time_t	day,
				mytime,
				prevtime,
				boundary,
				beforetime,
				aftertime;
	long int	before_gmtoff,
				after_gmtoff;
	int			before_isdst,
				after_isdst;
	int			res;

	if (tzp == session_timezone && HasCTZSet)
	{
		tm->tm_isdst = 0;		/* for lack of a better idea */
		return CTimeZone;
	}

	/*
	 * First, generate the pg_time_t value corresponding to the given
	 * y/m/d/h/m/s taken as GMT time.  If this overflows, punt and decide the
	 * timezone is GMT.  (We only need to worry about overflow on machines
	 * where pg_time_t is 32 bits.)
	 */
	if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
		goto overflow;
	date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE;

	day = ((pg_time_t) date) * SECS_PER_DAY;
	if (day / SECS_PER_DAY != date)
		goto overflow;
	sec = tm->tm_sec + (tm->tm_min + tm->tm_hour * MINS_PER_HOUR) * SECS_PER_MINUTE;
	mytime = day + sec;
	/* since sec >= 0, overflow could only be from +day to -mytime */
	if (mytime < 0 && day > 0)
		goto overflow;

	/*
	 * Find the DST time boundary just before or following the target time. We
	 * assume that all zones have GMT offsets less than 24 hours, and that DST
	 * boundaries can't be closer together than 48 hours, so backing up 24
	 * hours and finding the "next" boundary will work.
	 */
	prevtime = mytime - SECS_PER_DAY;
	if (mytime < 0 && prevtime > 0)
		goto overflow;

	res = pg_next_dst_boundary(&prevtime,
							   &before_gmtoff, &before_isdst,
							   &boundary,
							   &after_gmtoff, &after_isdst,
							   tzp);
	if (res < 0)
		goto overflow;			/* failure? */

	if (res == 0)
	{
		/* Non-DST zone, life is simple */
		tm->tm_isdst = before_isdst;
		return -(int) before_gmtoff;
	}

	/*
	 * Form the candidate pg_time_t values with local-time adjustment
	 */
	beforetime = mytime - before_gmtoff;
	if ((before_gmtoff > 0 &&
		 mytime < 0 && beforetime > 0) ||
		(before_gmtoff <= 0 &&
		 mytime > 0 && beforetime < 0))
		goto overflow;
	aftertime = mytime - after_gmtoff;
	if ((after_gmtoff > 0 &&
		 mytime < 0 && aftertime > 0) ||
		(after_gmtoff <= 0 &&
		 mytime > 0 && aftertime < 0))
		goto overflow;

	/*
	 * If both before or both after the boundary time, we know what to do
	 */
	if (beforetime <= boundary && aftertime < boundary)
	{
		tm->tm_isdst = before_isdst;
		return -(int) before_gmtoff;
	}
	if (beforetime > boundary && aftertime >= boundary)
	{
		tm->tm_isdst = after_isdst;
		return -(int) after_gmtoff;
	}

	/*
	 * It's an invalid or ambiguous time due to timezone transition. Prefer
	 * the standard-time interpretation.
	 */
	if (after_isdst == 0)
	{
		tm->tm_isdst = after_isdst;
		return -(int) after_gmtoff;
	}
	tm->tm_isdst = before_isdst;
	return -(int) before_gmtoff;

overflow:
	/* Given date is out of range, so assume UTC */
	tm->tm_isdst = 0;
	return 0;
}


/* DecodeTimeOnly()
 * Interpret parsed string as time fields only.
 * Returns 0 if successful, DTERR code if bogus input detected.
 *
 * Note that support for time zone is here for
 * SQL92 TIME WITH TIME ZONE, but it reveals
 * bogosity with SQL92 date/time standards, since
 * we must infer a time zone from current time.
 * - thomas 2000-03-10
 * Allow specifying date to get a better time zone,
 * if time zones are allowed. - thomas 2001-12-26
 */
int
DecodeTimeOnly(char **field, int *ftype, int nf,
			   int *dtype, struct pg_tm * tm, fsec_t *fsec, int *tzp)
{
	int			fmask = 0,
				tmask,
				type;
	int			ptype = 0;		/* "prefix type" for ISO h04mm05s06 format */
	int			i;
	int			val;
	int			dterr;
	bool		is2digits = FALSE;
	bool		bc = FALSE;
	int			mer = HR24;
	pg_tz	   *namedTz = NULL;

	*dtype = DTK_TIME;
	tm->tm_hour = 0;
	tm->tm_min = 0;
	tm->tm_sec = 0;
	*fsec = 0;
	/* don't know daylight savings time status apriori */
	tm->tm_isdst = -1;

	if (tzp != NULL)
		*tzp = 0;

	for (i = 0; i < nf; i++)
	{
		switch (ftype[i])
		{
			case DTK_DATE:

				/*
				 * Time zone not allowed? Then should not accept dates or time
				 * zones no matter what else!
				 */
				if (tzp == NULL)
					return DTERR_BAD_FORMAT;

				/* Under limited circumstances, we will accept a date... */
				if (i == 0 && nf >= 2 &&
					(ftype[nf - 1] == DTK_DATE || ftype[1] == DTK_TIME))
				{
					dterr = DecodeDate(field[i], fmask,
									   &tmask, &is2digits, tm);
					if (dterr)
						return dterr;
				}
				/* otherwise, this is a time and/or time zone */
				else
				{
					if (isdigit((unsigned char) *field[i]))
					{
						char	   *cp;

						/*
						 * Starts with a digit but we already have a time
						 * field? Then we are in trouble with time already...
						 */
						if ((fmask & DTK_TIME_M) == DTK_TIME_M)
							return DTERR_BAD_FORMAT;

						/*
						 * Should not get here and fail. Sanity check only...
						 */
						if ((cp = strchr(field[i], '-')) == NULL)
							return DTERR_BAD_FORMAT;

						/* Get the time zone from the end of the string */
						dterr = DecodeTimezone(cp, tzp);
						if (dterr)
							return dterr;
						*cp = '\0';

						/*
						 * Then read the rest of the field as a concatenated
						 * time
						 */
						dterr = DecodeNumberField(strlen(field[i]), field[i],
												  (fmask | DTK_DATE_M),
												  &tmask, tm,
												  fsec, &is2digits);
						if (dterr < 0)
							return dterr;
						ftype[i] = dterr;

						tmask |= DTK_M(TZ);
					}
					else
					{
						namedTz = pg_tzset(field[i]);
						if (!namedTz)
						{
							/*
							 * We should return an error code instead of
							 * ereport'ing directly, but then there is no way
							 * to report the bad time zone name.
							 */
							ereport(ERROR,
									(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
									 errmsg("time zone \"%s\" not recognized",
											field[i]),
													 errOmitLocation(true)));
						}
						/* we'll apply the zone setting below */
						ftype[i] = DTK_TZ;
						tmask = DTK_M(TZ);
					}
				}
				break;

			case DTK_TIME:
				dterr = DecodeTime(field[i], (fmask | DTK_DATE_M),
								   INTERVAL_FULL_RANGE,
								   &tmask, tm, fsec);
				if (dterr)
					return dterr;
				break;

			case DTK_TZ:
				{
					int			tz;

					if (tzp == NULL)
						return DTERR_BAD_FORMAT;

					dterr = DecodeTimezone(field[i], &tz);
					if (dterr)
						return dterr;
					*tzp = tz;
					tmask = DTK_M(TZ);
				}
				break;

			case DTK_NUMBER:

				/*
				 * Was this an "ISO time" with embedded field labels? An
				 * example is "h04m05s06" - thomas 2001-02-04
				 */
				if (ptype != 0)
				{
					char	   *cp;
					int			val;

					/* Only accept a date under limited circumstances */
					switch (ptype)
					{
						case DTK_JULIAN:
						case DTK_YEAR:
						case DTK_MONTH:
						case DTK_DAY:
							if (tzp == NULL)
								return DTERR_BAD_FORMAT;
						default:
							break;
					}

					errno = 0;
					val = strtoi(field[i], &cp, 10);
					if (errno == ERANGE)
						return DTERR_FIELD_OVERFLOW;

					/*
					 * only a few kinds are allowed to have an embedded
					 * decimal
					 */
					if (*cp == '.')
						switch (ptype)
						{
							case DTK_JULIAN:
							case DTK_TIME:
							case DTK_SECOND:
								break;
							default:
								return DTERR_BAD_FORMAT;
								break;
						}
					else if (*cp != '\0')
						return DTERR_BAD_FORMAT;

					switch (ptype)
					{
						case DTK_YEAR:
							tm->tm_year = val;
							tmask = DTK_M(YEAR);
							break;

						case DTK_MONTH:

							/*
							 * already have a month and hour? then assume
							 * minutes
							 */
							if ((fmask & DTK_M(MONTH)) != 0 &&
								(fmask & DTK_M(HOUR)) != 0)
							{
								tm->tm_min = val;
								tmask = DTK_M(MINUTE);
							}
							else
							{
								tm->tm_mon = val;
								tmask = DTK_M(MONTH);
							}
							break;

						case DTK_DAY:
							tm->tm_mday = val;
							tmask = DTK_M(DAY);
							break;

						case DTK_HOUR:
							tm->tm_hour = val;
							tmask = DTK_M(HOUR);
							break;

						case DTK_MINUTE:
							tm->tm_min = val;
							tmask = DTK_M(MINUTE);
							break;

						case DTK_SECOND:
							tm->tm_sec = val;
							tmask = DTK_M(SECOND);
							if (*cp == '.')
							{
								dterr = ParseFractionalSecond(cp, fsec);
								if (dterr)
									return dterr;
								tmask = DTK_ALL_SECS_M;
							}
							break;

						case DTK_TZ:
							tmask = DTK_M(TZ);
							dterr = DecodeTimezone(field[i], tzp);
							if (dterr)
								return dterr;
							break;

						case DTK_JULIAN:
							/***
							 * previous field was a label for "julian date"?
							 ***/
							tmask = DTK_DATE_M;
							j2date(val, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
							if (*cp == '.')
							{
								double		time;

								errno = 0;
								time = strtod(cp, &cp);
								if (*cp != '\0' || errno != 0)
									return DTERR_BAD_FORMAT;

#ifdef HAVE_INT64_TIMESTAMP
								time *= USECS_PER_DAY;
#else
								time *= SECS_PER_DAY;
#endif
								dt2time(time,
										&tm->tm_hour, &tm->tm_min,
										&tm->tm_sec, fsec);
								tmask |= DTK_TIME_M;
							}
							break;

						case DTK_TIME:
							/* previous field was "t" for ISO time */
							dterr = DecodeNumberField(strlen(field[i]), field[i],
													  (fmask | DTK_DATE_M),
													  &tmask, tm,
													  fsec, &is2digits);
							if (dterr < 0)
								return dterr;
							ftype[i] = dterr;

							if (tmask != DTK_TIME_M)
								return DTERR_BAD_FORMAT;
							break;

						default:
							return DTERR_BAD_FORMAT;
							break;
					}

					ptype = 0;
					*dtype = DTK_DATE;
				}
				else
				{
					char	   *cp;
					int			flen;

					flen = strlen(field[i]);
					cp = strchr(field[i], '.');

					/* Embedded decimal? */
					if (cp != NULL)
					{
						/*
						 * Under limited circumstances, we will accept a
						 * date...
						 */
						if (i == 0 && nf >= 2 && ftype[nf - 1] == DTK_DATE)
						{
							dterr = DecodeDate(field[i], fmask,
											   &tmask, &is2digits, tm);
							if (dterr)
								return dterr;
						}
						/* embedded decimal and several digits before? */
						else if (flen - strlen(cp) > 2)
						{
							/*
							 * Interpret as a concatenated date or time Set
							 * the type field to allow decoding other fields
							 * later. Example: 20011223 or 040506
							 */
							dterr = DecodeNumberField(flen, field[i],
													  (fmask | DTK_DATE_M),
													  &tmask, tm,
													  fsec, &is2digits);
							if (dterr < 0)
								return dterr;
							ftype[i] = dterr;
						}
						else
							return DTERR_BAD_FORMAT;
					}
					else if (flen > 4)
					{
						dterr = DecodeNumberField(flen, field[i],
												  (fmask | DTK_DATE_M),
												  &tmask, tm,
												  fsec, &is2digits);
						if (dterr < 0)
							return dterr;
						ftype[i] = dterr;
					}
					/* otherwise it is a single date/time field... */
					else
					{
						dterr = DecodeNumber(flen, field[i],
											 FALSE,
											 (fmask | DTK_DATE_M),
											 &tmask, tm,
											 fsec, &is2digits);
						if (dterr)
							return dterr;
					}
				}
				break;

			case DTK_STRING:
			case DTK_SPECIAL:
				type = DecodeSpecial(i, field[i], &val);
				if (type == IGNORE_DTF)
					continue;

				tmask = DTK_M(type);
				switch (type)
				{
					case RESERV:
						switch (val)
						{
							case DTK_CURRENT:
								ereport(ERROR,
									 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
									  errmsg("date/time value \"current\" is no longer supported")));
								return DTERR_BAD_FORMAT;
								break;

							case DTK_NOW:
								tmask = DTK_TIME_M;
								*dtype = DTK_TIME;
								GetCurrentTimeUsec(tm, fsec, NULL);
								break;

							case DTK_ZULU:
								tmask = (DTK_TIME_M | DTK_M(TZ));
								*dtype = DTK_TIME;
								tm->tm_hour = 0;
								tm->tm_min = 0;
								tm->tm_sec = 0;
								tm->tm_isdst = 0;
								break;

							default:
								return DTERR_BAD_FORMAT;
						}

						break;

					case DTZMOD:

						/*
						 * daylight savings time modifier (solves "MET DST"
						 * syntax)
						 */
						tmask |= DTK_M(DTZ);
						tm->tm_isdst = 1;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp += val * MINS_PER_HOUR;
						break;

					case DTZ:

						/*
						 * set mask for TZ here _or_ check for DTZ later when
						 * getting default timezone
						 */
						tmask |= DTK_M(TZ);
						tm->tm_isdst = 1;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp = val * MINS_PER_HOUR;
						ftype[i] = DTK_TZ;
						break;

					case TZ:
						tm->tm_isdst = 0;
						if (tzp == NULL)
							return DTERR_BAD_FORMAT;
						*tzp = val * MINS_PER_HOUR;
						ftype[i] = DTK_TZ;
						break;

					case IGNORE_DTF:
						break;

					case AMPM:
						mer = val;
						break;

					case ADBC:
						bc = (val == BC);
						break;

					case UNITS:
						tmask = 0;
						ptype = val;
						break;

					case ISOTIME:
						tmask = 0;

						/***
						 * We will need one of the following fields:
						 *	DTK_NUMBER should be hhmmss.fff
						 *	DTK_TIME should be hh:mm:ss.fff
						 *	DTK_DATE should be hhmmss-zz
						 ***/
						if (i >= nf - 1 ||
							(ftype[i + 1] != DTK_NUMBER &&
							 ftype[i + 1] != DTK_TIME &&
							 ftype[i + 1] != DTK_DATE))
							return DTERR_BAD_FORMAT;

						ptype = val;
						break;

					case UNKNOWN_FIELD:

						/*
						 * Before giving up and declaring error, check to see
						 * if it is an all-alpha timezone name.
						 */
						namedTz = pg_tzset(field[i]);
						if (!namedTz)
							return DTERR_BAD_FORMAT;
						/* we'll apply the zone setting below */
						tmask = DTK_M(TZ);
						break;

					default:
						return DTERR_BAD_FORMAT;
				}
				break;

			default:
				return DTERR_BAD_FORMAT;
		}

		if (tmask & fmask)
			return DTERR_BAD_FORMAT;
		fmask |= tmask;
	}				/* end loop over fields */

	/* do final checking/adjustment of Y/M/D fields */
	dterr = ValidateDate(fmask, is2digits, bc, tm);
	if (dterr)
		return dterr;

	/* handle AM/PM */
	if (mer != HR24 && tm->tm_hour > 12)
		return DTERR_FIELD_OVERFLOW;
	if (mer == AM && tm->tm_hour == 12)
		tm->tm_hour = 0;
	else if (mer == PM && tm->tm_hour != 12)
		tm->tm_hour += 12;

	if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_min > 59 ||
		tm->tm_sec < 0 || tm->tm_sec > 60 || tm->tm_hour > 24 ||
		/* test for > 24:00:00 */
		(tm->tm_hour == 24 &&
		 (tm->tm_min > 0 || tm->tm_sec > 0 || *fsec > 0)) ||
#ifdef HAVE_INT64_TIMESTAMP
		*fsec < INT64CONST(0) || *fsec > USECS_PER_SEC
#else
		*fsec < 0 || *fsec > 1
#endif
		)
		return DTERR_FIELD_OVERFLOW;

	if ((fmask & DTK_TIME_M) != DTK_TIME_M)
		return DTERR_BAD_FORMAT;

	/*
	 * If we had a full timezone spec, compute the offset (we could not do it
	 * before, because we may need the date to resolve DST status).
	 */
	if (namedTz != NULL)
	{
		long int	gmtoff;

		/* daylight savings time modifier disallowed with full TZ */
		if (fmask & DTK_M(DTZMOD))
			return DTERR_BAD_FORMAT;

		/* if non-DST zone, we do not need to know the date */
		if (pg_get_timezone_offset(namedTz, &gmtoff))
		{
			*tzp = -(int) gmtoff;
		}
		else
		{
			/* a date has to be specified */
			if ((fmask & DTK_DATE_M) != DTK_DATE_M)
				return DTERR_BAD_FORMAT;
			*tzp = DetermineTimeZoneOffset(tm, namedTz);
		}
	}

	/* timezone not specified? then find local timezone if possible */
	if (tzp != NULL && !(fmask & DTK_M(TZ)))
	{
		struct pg_tm tt,
				   *tmp = &tt;

		/*
		 * daylight savings time modifier but no standard timezone? then error
		 */
		if (fmask & DTK_M(DTZMOD))
			return DTERR_BAD_FORMAT;

		if ((fmask & DTK_DATE_M) == 0)
			GetCurrentDateTime(tmp);
		else
		{
			tmp->tm_year = tm->tm_year;
			tmp->tm_mon = tm->tm_mon;
			tmp->tm_mday = tm->tm_mday;
		}
		tmp->tm_hour = tm->tm_hour;
		tmp->tm_min = tm->tm_min;
		tmp->tm_sec = tm->tm_sec;
		*tzp = DetermineTimeZoneOffset(tmp, session_timezone);
		tm->tm_isdst = tmp->tm_isdst;
	}

	return 0;
}

/* DecodeDate()
 * Decode date string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 *	str: field to be parsed
 *	fmask: bitmask for field types already seen
 *	*tmask: receives bitmask for fields found here
 *	*is2digits: set to TRUE if we find 2-digit year
 *	*tm: field values are stored into appropriate members of this struct
 */
static int
DecodeDate(char *str, int fmask, int *tmask, bool *is2digits,
		   struct pg_tm * tm)
{
	fsec_t		fsec;
	int			nf = 0;
	int			i,
				len;
	int			dterr;
	bool		haveTextMonth = FALSE;
	int			type,
				val,
				dmask = 0;
	char	   *field[MAXDATEFIELDS];
	int			fieldlens[MAXDATEFIELDS];

	*tmask = 0;

	/* parse this string... */
	while (*str != '\0' && nf < MAXDATEFIELDS)
	{
		/* skip field separators */
		while (!isalnum((unsigned char) *str))
			str++;

		field[nf] = str;
		if (isdigit((unsigned char) *str))
		{
			while (isdigit((unsigned char) *str))
				str++;
		}
		else if (isalpha((unsigned char) *str))
		{
			while (isalpha((unsigned char) *str))
				str++;
		}

		fieldlens[nf] = str - field[nf];
		/* Just get rid of any non-digit, non-alpha characters... */
		if (*str != '\0')
			*str++ = '\0';
		nf++;
	}

	/* look first for text fields, since that will be unambiguous month */
	for (i = 0; i < nf; i++)
	{
		if (isalpha((unsigned char) *field[i]))
		{
			type = DecodeSpecial(i, field[i], &val);
			if (type == IGNORE_DTF)
				continue;

			dmask = DTK_M(type);
			switch (type)
			{
				case MONTH:
					tm->tm_mon = val;
					haveTextMonth = TRUE;
					break;

				default:
					return DTERR_BAD_FORMAT;
			}
			if (fmask & dmask)
				return DTERR_BAD_FORMAT;

			fmask |= dmask;
			*tmask |= dmask;

			/* mark this field as being completed */
			field[i] = NULL;
		}
	}

	/* now pick up remaining numeric fields */
	for (i = 0; i < nf; i++)
	{
		if (field[i] == NULL)
			continue;

		if ((len = fieldlens[i]) <= 0)
			return DTERR_BAD_FORMAT;

		dterr = DecodeNumber(len, field[i], haveTextMonth, fmask,
							 &dmask, tm,
							 &fsec, is2digits);
		if (dterr)
			return dterr;

		if (fmask & dmask)
			return DTERR_BAD_FORMAT;

		fmask |= dmask;
		*tmask |= dmask;
	}

	if ((fmask & ~(DTK_M(DOY) | DTK_M(TZ))) != DTK_DATE_M)
		return DTERR_BAD_FORMAT;

	/* validation of the field values must wait until ValidateDate() */

	return 0;
}

/* ValidateDate()
 * Check valid year/month/day values, handle BC and DOY cases
 * Return 0 if okay, a DTERR code if not.
 */
static int
ValidateDate(int fmask, bool is2digits, bool bc, struct pg_tm * tm)
{
	if (fmask & DTK_M(YEAR))
	{
		if (bc)
		{
			/* there is no year zero in AD/BC notation */
			if (tm->tm_year <= 0)
				return DTERR_FIELD_OVERFLOW;
			/* internally, we represent 1 BC as year zero, 2 BC as -1, etc */
				tm->tm_year = -(tm->tm_year - 1);
		}
		else if (is2digits)
		{
			/* process 1 or 2-digit input as 1970-2069 AD, allow '0' and '00' */
			if (tm->tm_year < 0)				/* just paranoia */
				return DTERR_FIELD_OVERFLOW;
			if (tm->tm_year < 70)
				tm->tm_year += 2000;
			else if (tm->tm_year < 100)
				tm->tm_year += 1900;
		}
		else
		{
			/* there is no year zero in AD/BC notation */
			if (tm->tm_year <= 0)
				return DTERR_FIELD_OVERFLOW;
		}
	}

	/* now that we have correct year, decode DOY */
	if (fmask & DTK_M(DOY))
	{
		j2date(date2j(tm->tm_year, 1, 1) + tm->tm_yday - 1,
			   &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
	}

	/* check for valid month */
	if (fmask & DTK_M(MONTH))
	{
		if (tm->tm_mon < 1 || tm->tm_mon > MONTHS_PER_YEAR)
			return DTERR_MD_FIELD_OVERFLOW;
	}

	/* minimal check for valid day */
	if (fmask & DTK_M(DAY))
	{
		if (tm->tm_mday < 1 || tm->tm_mday > 31)
			return DTERR_MD_FIELD_OVERFLOW;
	}

	if ((fmask & DTK_DATE_M) == DTK_DATE_M)
	{
		/*
		 * Check for valid day of month, now that we know for sure the month
		 * and year.  Note we don't use MD_FIELD_OVERFLOW here, since it seems
		 * unlikely that "Feb 29" is a YMD-order error.
		 */
		if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
			return DTERR_FIELD_OVERFLOW;
	}

	return 0;
}


/* DecodeTime()
 * Decode time string which includes delimiters.
 * Return 0 if okay, a DTERR code if not.
 *
 * Only check the lower limit on hours, since this same code can be
 * used to represent time spans.
 */
static int
DecodeTime(char *str, int fmask, int range,
		   int *tmask, struct pg_tm * tm, fsec_t *fsec)
{
	char	   *cp;
	int			dterr;

	*tmask = DTK_TIME_M;

	errno = 0;
	tm->tm_hour = strtoi(str, &cp, 10);
	if (errno == ERANGE)
		return DTERR_FIELD_OVERFLOW;
	if (*cp != ':')
		return DTERR_BAD_FORMAT;
	errno = 0;
	tm->tm_min = strtoi(cp + 1, &cp, 10);
	if (errno == ERANGE)
		return DTERR_FIELD_OVERFLOW;
	if (*cp == '\0')
	{
		tm->tm_sec = 0;
		*fsec = 0;
		/* If it's a MINUTE TO SECOND interval, take 2 fields as being mm:ss */
		if (range == (INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND)))
		{
			tm->tm_sec = tm->tm_min;
			tm->tm_min = tm->tm_hour;
			tm->tm_hour = 0;
		}
	}
	else if (*cp == '.')
	{
		/* always assume mm:ss.sss is MINUTE TO SECOND */
		dterr = ParseFractionalSecond(cp, fsec);
		if (dterr)
			return dterr;
		tm->tm_sec = tm->tm_min;
		tm->tm_min = tm->tm_hour;
		tm->tm_hour = 0;
	}
	else if (*cp == ':')
	{
		errno = 0;
		tm->tm_sec = strtoi(cp + 1, &cp, 10);
		if (errno == ERANGE)
			return DTERR_FIELD_OVERFLOW;
		if (*cp == '\0')
			*fsec = 0;
		else if (*cp == '.')
		{
			dterr = ParseFractionalSecond(cp, fsec);
			if (dterr)
				return dterr;
		}
		else
				return DTERR_BAD_FORMAT;
		}
		else
			return DTERR_BAD_FORMAT;

	/* do a sanity check */
#ifdef HAVE_INT64_TIMESTAMP
	if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_min > 59 ||
		tm->tm_sec < 0 || tm->tm_sec > 60 || *fsec < INT64CONST(0) ||
		*fsec > USECS_PER_SEC)
		return DTERR_FIELD_OVERFLOW;
#else
	if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_min > 59 ||
		tm->tm_sec < 0 || tm->tm_sec > 60 || *fsec < 0 || *fsec > 1)
		return DTERR_FIELD_OVERFLOW;
#endif

	return 0;
}


/* DecodeNumber()
 * Interpret plain numeric field as a date value in context.
 * Return 0 if okay, a DTERR code if not.
 */
static int
DecodeNumber(int flen, char *str, bool haveTextMonth, int fmask,
			 int *tmask, struct pg_tm * tm, fsec_t *fsec, bool *is2digits)
{
	int			val;
	char	   *cp;
	int			dterr;

	*tmask = 0;

	errno = 0;
	val = strtoi(str, &cp, 10);
	if (errno == ERANGE)
		return DTERR_FIELD_OVERFLOW;
	if (cp == str)
		return DTERR_BAD_FORMAT;

	if (*cp == '.')
	{
		/*
		 * More than two digits before decimal point? Then could be a date or
		 * a run-together time: 2001.360 20011225 040506.789
		 */
		if (cp - str > 2)
		{
			dterr = DecodeNumberField(flen, str,
									  (fmask | DTK_DATE_M),
									  tmask, tm,
									  fsec, is2digits);
			if (dterr < 0)
				return dterr;
			return 0;
		}

		dterr = ParseFractionalSecond(cp, fsec);
		if (dterr)
			return dterr;
	}
	else if (*cp != '\0')
		return DTERR_BAD_FORMAT;

	/* Special case for day of year */
	if (flen == 3 && (fmask & DTK_DATE_M) == DTK_M(YEAR) && val >= 1 &&
		val <= 366)
	{
		*tmask = (DTK_M(DOY) | DTK_M(MONTH) | DTK_M(DAY));
		tm->tm_yday = val;
		/* tm_mon and tm_mday can't actually be set yet ... */
		return 0;
	}

	/* Switch based on what we have so far */
	switch (fmask & DTK_DATE_M)
	{
		case 0:

			/*
			 * Nothing so far; make a decision about what we think the input
			 * is.	There used to be lots of heuristics here, but the
			 * consensus now is to be paranoid.  It *must* be either
			 * YYYY-MM-DD (with a more-than-two-digit year field), or the
			 * field order defined by DateOrder.
			 */
			if (flen >= 3 || DateOrder == DATEORDER_YMD)
			{
				*tmask = DTK_M(YEAR);
				tm->tm_year = val;
			}
			else if (DateOrder == DATEORDER_DMY)
			{
				*tmask = DTK_M(DAY);
				tm->tm_mday = val;
			}
			else
			{
				*tmask = DTK_M(MONTH);
				tm->tm_mon = val;
			}
			break;

		case (DTK_M(YEAR)):
			/* Must be at second field of YY-MM-DD */
			*tmask = DTK_M(MONTH);
			tm->tm_mon = val;
			break;

		case (DTK_M(MONTH)):
			if (haveTextMonth)
			{
				/*
				 * We are at the first numeric field of a date that included a
				 * textual month name.	We want to support the variants
				 * MON-DD-YYYY, DD-MON-YYYY, and YYYY-MON-DD as unambiguous
				 * inputs.	We will also accept MON-DD-YY or DD-MON-YY in
				 * either DMY or MDY modes, as well as YY-MON-DD in YMD mode.
				 */
				if (flen >= 3 || DateOrder == DATEORDER_YMD)
				{
					*tmask = DTK_M(YEAR);
					tm->tm_year = val;
				}
				else
				{
					*tmask = DTK_M(DAY);
					tm->tm_mday = val;
				}
			}
			else
			{
				/* Must be at second field of MM-DD-YY */
				*tmask = DTK_M(DAY);
				tm->tm_mday = val;
			}
			break;

		case (DTK_M(YEAR) | DTK_M(MONTH)):
			if (haveTextMonth)
			{
				/* Need to accept DD-MON-YYYY even in YMD mode */
				if (flen >= 3 && *is2digits)
				{
					/* Guess that first numeric field is day was wrong */
					*tmask = DTK_M(DAY);		/* YEAR is already set */
					tm->tm_mday = tm->tm_year;
					tm->tm_year = val;
					*is2digits = FALSE;
				}
				else
				{
					*tmask = DTK_M(DAY);
					tm->tm_mday = val;
				}
			}
			else
			{
				/* Must be at third field of YY-MM-DD */
				*tmask = DTK_M(DAY);
				tm->tm_mday = val;
			}
			break;

		case (DTK_M(DAY)):
			/* Must be at second field of DD-MM-YY */
			*tmask = DTK_M(MONTH);
			tm->tm_mon = val;
			break;

		case (DTK_M(MONTH) | DTK_M(DAY)):
			/* Must be at third field of DD-MM-YY or MM-DD-YY */
			*tmask = DTK_M(YEAR);
			tm->tm_year = val;
			break;

		case (DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY)):
			/* we have all the date, so it must be a time field */
			dterr = DecodeNumberField(flen, str, fmask,
									  tmask, tm,
									  fsec, is2digits);
			if (dterr < 0)
				return dterr;
			return 0;

		default:
			/* Anything else is bogus input */
			return DTERR_BAD_FORMAT;
	}

	/*
	 * When processing a year field, mark it for adjustment if it's only one
	 * or two digits.
	 */
	if (*tmask == DTK_M(YEAR))
		*is2digits = (flen <= 2);

	return 0;
}


/* DecodeNumberField()
 * Interpret numeric string as a concatenated date or time field.
 * Return a DTK token (>= 0) if successful, a DTERR code (< 0) if not.
 *
 * Use the context of previously decoded fields to help with
 * the interpretation.
 */
static int
DecodeNumberField(int len, char *str, int fmask,
				int *tmask, struct pg_tm * tm, fsec_t *fsec, bool *is2digits)
{
	char	   *cp;
	bool		have_frac = false;

	/*
	 * Have a decimal point? Then this is a date or something with a seconds
	 * field...
	 */
	if ((cp = strchr(str, '.')) != NULL)
	{
		/*
		 * Can we use ParseFractionalSecond here?  Not clear whether trailing
		 * junk should be rejected ...
		 */
		double		frac;

		have_frac = true;
		errno = 0;
		frac = strtod(cp, NULL);
		if (errno != 0)
			return DTERR_BAD_FORMAT;
#ifdef HAVE_INT64_TIMESTAMP
		*fsec = rint(frac * 1000000);
#else
		*fsec = frac;
#endif
		/* Now truncate off the fraction for further processing */
		*cp = '\0';
		len = strlen(str);
	}
	/* No decimal point and no complete date yet? */
	if ((fmask & DTK_DATE_M) != DTK_DATE_M && len <= 8 && !have_frac)
	{
		/* yyyymmdd? */
		if (len == 8)
		{
			*tmask = DTK_DATE_M;

			tm->tm_mday = atoi(str + 6);
			*(str + 6) = '\0';
			tm->tm_mon = atoi(str + 4);
			*(str + 4) = '\0';
			tm->tm_year = atoi(str + 0);

			return DTK_DATE;
		}
		/* yymmdd? */
		else if (len == 6)
		{
			*tmask = DTK_DATE_M;
			tm->tm_mday = atoi(str + 4);
			*(str + 4) = '\0';
			tm->tm_mon = atoi(str + 2);
			*(str + 2) = '\0';
			tm->tm_year = atoi(str + 0);
			*is2digits = TRUE;

			return DTK_DATE;
		}
	}
	else if ((fmask & DTK_DATE_M) != DTK_DATE_M && 
			 (fmask & DTK_TIME_M) != DTK_TIME_M)
	{
        /* yyyymmddhhmmss? */ 
        if (len == 14) 
        { 
            *tmask = DTK_DATE_M | DTK_TIME_M; 

            tm->tm_sec = atoi(str + 12); 
            *(str + 12) = '\0'; 
            tm->tm_min = atoi(str + 10); 
            *(str + 10) = '\0'; 
            tm->tm_hour = atoi(str + 8); 
            *(str + 8) = '\0'; 
            tm->tm_mday = atoi(str + 6); 
            *(str + 6) = '\0'; 
            tm->tm_mon = atoi(str + 4); 
            *(str + 4) = '\0'; 
            tm->tm_year = atoi(str + 0); 
            return DTK_DATE; 
        } 
	}

	/* not all time fields are specified? */
	if ((fmask & DTK_TIME_M) != DTK_TIME_M)
	{
		/* hhmmss */
		if (len == 6)
		{
			*tmask = DTK_TIME_M;
			tm->tm_sec = atoi(str + 4);
			*(str + 4) = '\0';
			tm->tm_min = atoi(str + 2);
			*(str + 2) = '\0';
			tm->tm_hour = atoi(str + 0);

			return DTK_TIME;
		}
		/* hhmm? */
		else if (len == 4)
		{
			*tmask = DTK_TIME_M;
			tm->tm_sec = 0;
			tm->tm_min = atoi(str + 2);
			*(str + 2) = '\0';
			tm->tm_hour = atoi(str + 0);

			return DTK_TIME;
		}
	}

	return DTERR_BAD_FORMAT;
}


/* DecodeTimezone()
 * Interpret string as a numeric timezone.
 *
 * Return 0 if okay (and set *tzp), a DTERR code if not okay.
 *
 * NB: this must *not* ereport on failure; see commands/variable.c.
 *
 * Note: we allow timezone offsets up to 13:59.  There are places that
 * use +1300 summer time.
 */
static int
DecodeTimezone(char *str, int *tzp)
{
	int			tz;
	int			hr,
				min,
				sec = 0;
	char	   *cp;

	/* leading character must be "+" or "-" */
	if (*str != '+' && *str != '-')
		return DTERR_BAD_FORMAT;

	errno = 0;
	hr = strtoi(str + 1, &cp, 10);
	if (errno == ERANGE)
		return DTERR_TZDISP_OVERFLOW;

	/* explicit delimiter? */
	if (*cp == ':')
	{
		errno = 0;
		min = strtoi(cp + 1, &cp, 10);
		if (errno == ERANGE)
			return DTERR_TZDISP_OVERFLOW;
		if (*cp == ':')
		{
			errno = 0;
			sec = strtoi(cp + 1, &cp, 10);
			if (errno == ERANGE)
				return DTERR_TZDISP_OVERFLOW;
		}
	}
	/* otherwise, might have run things together... */
	else if (*cp == '\0' && strlen(str) > 3)
	{
		min = hr % 100;
		hr = hr / 100;
		/* we could, but don't, support a run-together hhmmss format */
	}
	else
		min = 0;

	if (hr < 0 || hr > 14)
		return DTERR_TZDISP_OVERFLOW;
	if (min < 0 || min >= 60)
		return DTERR_TZDISP_OVERFLOW;
	if (sec < 0 || sec >= 60)
		return DTERR_TZDISP_OVERFLOW;

	tz = (hr * MINS_PER_HOUR + min) * SECS_PER_MINUTE + sec;
	if (*str == '-')
		tz = -tz;

	*tzp = -tz;

	if (*cp != '\0')
		return DTERR_BAD_FORMAT;

	return 0;
}

/* DecodeSpecial()
 * Decode text string using lookup table.
 *
 * Implement a cache lookup since it is likely that dates
 *	will be related in format.
 *
 * NB: this must *not* ereport on failure;
 * see commands/variable.c.
 */
int
DecodeSpecial(int field, char *lowtoken, int *val)
{
	int			type;
	const datetkn *tp;

	tp = datecache[field];
	if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
	{
		tp = datebsearch(lowtoken, timezonetktbl, sztimezonetktbl);
		if (tp == NULL)
			tp = datebsearch(lowtoken, datetktbl, szdatetktbl);
	}
	if (tp == NULL)
	{
		type = UNKNOWN_FIELD;
		*val = 0;
	}
	else
	{
		datecache[field] = tp;
		type = tp->type;
		switch (type)
		{
			case TZ:
			case DTZ:
			case DTZMOD:
				*val = FROMVAL(tp);
				break;

			default:
				*val = tp->value;
				break;
		}
	}

	return type;
}


/* ClearPgTM
 *
 * Zero out a pg_tm and associated fsec_t
 */
static inline void 
ClearPgTm(struct pg_tm *tm, fsec_t *fsec)
{
	tm->tm_year = 0;
	tm->tm_mon  = 0;
	tm->tm_mday = 0;
	tm->tm_hour = 0;
	tm->tm_min  = 0;
	tm->tm_sec  = 0;
	*fsec       = 0;
}


/* DecodeInterval()
 * Interpret previously parsed fields for general time interval.
 * Returns 0 if successful, DTERR code if bogus input detected.
 * dtype, tm, fsec are output parameters.
 *
 * Allow "date" field DTK_DATE since this could be just
 *	an unsigned floating point number. - thomas 1997-11-16
 *
 * Allow ISO-style time span, with implicit units on number of days
 *	preceding an hh:mm:ss field. - thomas 1998-04-30
 */
int
DecodeInterval(char **field, int *ftype, int nf, int range,
			   int *dtype, struct pg_tm * tm, fsec_t *fsec)
{
	bool		is_before = FALSE;
	char	   *cp;
	int			fmask = 0,
				tmask,
				type;
	int			i;
	int			dterr;
	int			val;
	double		fval;

	*dtype = DTK_DELTA;
	type = IGNORE_DTF;
	ClearPgTm(tm,fsec);

	/* read through list backwards to pick up units before values */
	for (i = nf - 1; i >= 0; i--)
	{
		switch (ftype[i])
		{
			case DTK_TIME:
				dterr = DecodeTime(field[i], fmask, range,
								   &tmask, tm, fsec);
				if (dterr)
					return dterr;
				type = DTK_DAY;
				break;

			case DTK_TZ:

				/*
				 * Timezone is a token with a leading sign character and at
				 * least one digit; there could be ':', '.', '-' embedded in
				 * it as well.
				 */
				Assert(*field[i] == '-' || *field[i] == '+');

				/*
				 * Try for hh:mm or hh:mm:ss.  If not, fall through to
				 * DTK_NUMBER case, which can handle signed float numbers and
				 * signed year-month values.
				 */
				if (strchr(field[i] + 1, ':') != NULL &&
					DecodeTime(field[i] + 1, fmask, INTERVAL_FULL_RANGE,
							   &tmask, tm, fsec) == 0)
				{
					if (*field[i] == '-')
					{
						/* flip the sign on all fields */
						tm->tm_hour = -tm->tm_hour;
						tm->tm_min = -tm->tm_min;
						tm->tm_sec = -tm->tm_sec;
						*fsec = -(*fsec);
					}

					/*
					 * Set the next type to be a day, if units are not
					 * specified. This handles the case of '1 +02:03' since we
					 * are reading right to left.
					 */
					type = DTK_DAY;
					tmask = DTK_M(TZ);
					break;
				}
				/* FALL THROUGH */

			case DTK_DATE:
			case DTK_NUMBER:
				if (type == IGNORE_DTF)
				{
					/* use typmod to decide what rightmost field is */
					switch (range)
					{
						case INTERVAL_MASK(YEAR):
							type = DTK_YEAR;
							break;
						case INTERVAL_MASK(MONTH):
						case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
							type = DTK_MONTH;
							break;
						case INTERVAL_MASK(DAY):
							type = DTK_DAY;
							break;
						case INTERVAL_MASK(HOUR):
						case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
							type = DTK_HOUR;
							break;
						case INTERVAL_MASK(MINUTE):
						case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
						case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
							type = DTK_MINUTE;
							break;
						case INTERVAL_MASK(SECOND):
						case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
						case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
						case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
							type = DTK_SECOND;
							break;
						default:
						type = DTK_SECOND;
							break;
					}
				}

				errno = 0;
				val = strtoi(field[i], &cp, 10);
				if (errno == ERANGE)
					return DTERR_FIELD_OVERFLOW;

				if (*cp == '-')
				{
					/* SQL "years-months" syntax */
					int		val2;

					val2 = strtoi(cp + 1, &cp, 10);
					if (errno == ERANGE || val2 < 0 || val2 >= MONTHS_PER_YEAR)
						return DTERR_FIELD_OVERFLOW;
					if (*cp != '\0')
						return DTERR_BAD_FORMAT;
					type = DTK_MONTH;
					if (*field[i] == '-')
						val2 = -val2;
					val = val * MONTHS_PER_YEAR + val2;
					fval = 0;
				}
				else if (*cp == '.')
				{
					errno = 0;
					fval = strtod(cp, &cp);
					if (*cp != '\0' || errno != 0)
						return DTERR_BAD_FORMAT;

					if (*field[i] == '-')
						fval = -fval;
				}
				else if (*cp == '\0')
					fval = 0;
				else
					return DTERR_BAD_FORMAT;

				tmask = 0;		/* DTK_M(type); */

				switch (type)
				{
					case DTK_MICROSEC:
#ifdef HAVE_INT64_TIMESTAMP
						*fsec += rint(val + fval);
#else
						*fsec += (val + fval) * 1e-6;
#endif
						tmask = DTK_M(MICROSECOND);
						break;

					case DTK_MILLISEC:
						/* avoid overflowing the fsec field */
						tm->tm_sec += val / 1000;
						val -= (val / 1000) * 1000;
#ifdef HAVE_INT64_TIMESTAMP
						*fsec += rint((val + fval) * 1000);
#else
						*fsec += (val + fval) * 1e-3;
#endif
						tmask = DTK_M(MILLISECOND);
						break;

					case DTK_SECOND:
						tm->tm_sec += val;
#ifdef HAVE_INT64_TIMESTAMP
						*fsec += rint(fval * 1000000);
#else
						*fsec += fval;
#endif

						/*
						 * If any subseconds were specified, consider this
						 * microsecond and millisecond input as well.
						 */
						if (fval == 0)
							tmask = DTK_M(SECOND);
						else
							tmask = DTK_ALL_SECS_M;
						break;

					case DTK_MINUTE:
						tm->tm_min += val;
						AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
						tmask = DTK_M(MINUTE);
						break;

					case DTK_HOUR:
						tm->tm_hour += val;
						AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
						tmask = DTK_M(HOUR);
						type = DTK_DAY;	/* set for next field */
						break;

					case DTK_DAY:
						tm->tm_mday += val;
						AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
						tmask = DTK_M(DAY);
						break;

					case DTK_WEEK:
						tm->tm_mday += val * 7;
						AdjustFractDays(fval, tm, fsec, 7);
						tmask = DTK_M(WEEK);
						break;

					case DTK_MONTH:
						tm->tm_mon += val;
						AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
						tmask = DTK_M(MONTH);
						break;

					case DTK_YEAR:
						tm->tm_year += val;
						if (fval != 0)
							tm->tm_mon += fval * MONTHS_PER_YEAR;
						tmask = DTK_M(YEAR);
						break;

					case DTK_DECADE:
						tm->tm_year += val * 10;
						if (fval != 0)
							tm->tm_mon += fval * MONTHS_PER_YEAR * 10;
						tmask = DTK_M(DECADE);
						break;

					case DTK_CENTURY:
						tm->tm_year += val * 100;
						if (fval != 0)
							tm->tm_mon += fval * MONTHS_PER_YEAR * 100;
						tmask = DTK_M(CENTURY);
						break;

					case DTK_MILLENNIUM:
						tm->tm_year += val * 1000;
						if (fval != 0)
							tm->tm_mon += fval * MONTHS_PER_YEAR * 1000;
						tmask = DTK_M(MILLENNIUM);
						break;

					default:
						return DTERR_BAD_FORMAT;
				}
				break;

			case DTK_STRING:
			case DTK_SPECIAL:
				type = DecodeUnits(i, field[i], &val);
				if (type == IGNORE_DTF)
					continue;

				tmask = 0;		/* DTK_M(type); */
				switch (type)
				{
					case UNITS:
						type = val;
						break;

					case AGO:
						is_before = TRUE;
						type = val;
						break;

					case RESERV:
						tmask = (DTK_DATE_M || DTK_TIME_M);
						*dtype = val;
						break;

					default:
						return DTERR_BAD_FORMAT;
				}
				break;

			default:
				return DTERR_BAD_FORMAT;
		}

		if (tmask & fmask)
			return DTERR_BAD_FORMAT;
		fmask |= tmask;
	}

	/* ensure that at least one time field has been found */
	if (fmask == 0)
				return DTERR_BAD_FORMAT;

	/* ensure fractional seconds are fractional */
	if (*fsec != 0)
	{
		int			sec;

#ifdef HAVE_INT64_TIMESTAMP
		sec = *fsec / USECS_PER_SEC;
		*fsec -= sec * USECS_PER_SEC;
#else
		TMODULO(*fsec, sec, 1.0);
#endif
		tm->tm_sec += sec;
	}

	/*----------
	 * The SQL standard defines the interval literal
	 *   '-1 1:00:00'
	 * to mean "negative 1 days and negative 1 hours", while Postgres
	 * traditionally treats this as meaning "negative 1 days and positive
	 * 1 hours".  In SQL_STANDARD intervalstyle, we apply the leading sign
	 * to all fields if there are no other explicit signs.
	 *
	 * We leave the signs alone if there are additional explicit signs.
	 * This protects us against misinterpreting postgres-style dump output,
	 * since the postgres-style output code has always put an explicit sign on
	 * all fields following a negative field.  But note that SQL-spec output
	 * is ambiguous and can be misinterpreted on load!  (So it's best practice
	 * to dump in postgres style, not SQL style.)
	 *----------
	 */
	if (IntervalStyle == INTSTYLE_SQL_STANDARD && *field[0] == '-')
	{
		/* Check for additional explicit signs */
		bool	more_signs = false;

		for (i = 1; i < nf; i++)
		{
			if (*field[i] == '-' || *field[i] == '+')
			{
				more_signs = true;
				break;
			}
		}

		if (!more_signs)
		{
			/*
			 * Rather than re-determining which field was field[0], just force
			 * 'em all negative.
			 */
			if (*fsec > 0)
				*fsec = -(*fsec);
			if (tm->tm_sec > 0)
				tm->tm_sec = -tm->tm_sec;
			if (tm->tm_min > 0)
				tm->tm_min = -tm->tm_min;
			if (tm->tm_hour > 0)
				tm->tm_hour = -tm->tm_hour;
			if (tm->tm_mday > 0)
				tm->tm_mday = -tm->tm_mday;
			if (tm->tm_mon > 0)
				tm->tm_mon = -tm->tm_mon;
			if (tm->tm_year > 0)
				tm->tm_year = -tm->tm_year;
		}
	}

	/* finally, AGO negates everything */
	if (is_before)
	{
		*fsec = -(*fsec);
		tm->tm_sec = -tm->tm_sec;
		tm->tm_min = -tm->tm_min;
		tm->tm_hour = -tm->tm_hour;
		tm->tm_mday = -tm->tm_mday;
		tm->tm_mon = -tm->tm_mon;
		tm->tm_year = -tm->tm_year;
	}

	return 0;
}


/*
 * Helper functions to avoid duplicated code in DecodeISO8601Interval.
 *
 * Parse a decimal value and break it into integer and fractional parts.
 * Returns 0 or DTERR code.
 */
static int
ParseISO8601Number(char *str, char **endptr, int *ipart, double *fpart)
{
	double		val;

	if (!(isdigit((unsigned char) *str) || *str == '-' || *str == '.'))
		return DTERR_BAD_FORMAT;
	errno = 0;
	val = strtod(str, endptr);
	/* did we not see anything that looks like a double? */
	if (*endptr == str || errno != 0)
		return DTERR_BAD_FORMAT;
	/* watch out for overflow */
	if (val < INT_MIN || val > INT_MAX)
		return DTERR_FIELD_OVERFLOW;
	/* be very sure we truncate towards zero (cf dtrunc()) */
	if (val >= 0)
		*ipart = (int) floor(val);
	else
		*ipart = (int) -floor(-val);
	*fpart = val - *ipart;
	return 0;
}

/*
 * Determine number of integral digits in a valid ISO 8601 number field
 * (we should ignore sign and any fraction part)
 */
static int
ISO8601IntegerWidth(char *fieldstart)
{
	/* We might have had a leading '-' */
	if (*fieldstart == '-')
		fieldstart++;
	return strspn(fieldstart, "0123456789");
}


/* DecodeISO8601Interval()
 *  Decode an ISO 8601 time interval of the "format with designators"
 *  (section 4.4.3.2) or "alternative format" (section 4.4.3.3)
 *  Examples:  P1D  for 1 day
 *             PT1H for 1 hour
 *             P2Y6M7DT1H30M for 2 years, 6 months, 7 days 1 hour 30 min
 *             P0002-06-07T01:30:00 the same value in alternative format
 *
 * Returns 0 if successful, DTERR code if bogus input detected.
 * Note: error code should be DTERR_BAD_FORMAT if input doesn't look like
 * ISO8601, otherwise this could cause unexpected error messages.
 * dtype, tm, fsec are output parameters.
 *
 *  A couple exceptions from the spec:
 *   - a week field ('W') may coexist with other units
 *   - allows decimals in fields other than the least significant unit.
 */
int
DecodeISO8601Interval(char *str,
					  int *dtype, struct pg_tm * tm, fsec_t *fsec)
{
	bool	datepart = true;
	bool	havefield = false;

	*dtype = DTK_DELTA;
	ClearPgTm(tm, fsec);

	if (strlen(str) < 2 || str[0] != 'P')
		return DTERR_BAD_FORMAT;

	str++;
	while (*str)
	{
		char   *fieldstart;
		int		val;
		double	fval;
		char    unit;
		int		dterr;

		if (*str == 'T') /* T indicates the beginning of the time part */
		{
			datepart = false;
			havefield = false;
			str++;
			continue;
		}

		fieldstart = str;
		dterr = ParseISO8601Number(str, &str, &val, &fval);
		if (dterr)
			return dterr;

		/*
		 * Note: we could step off the end of the string here.  Code below
		 * *must* exit the loop if unit == '\0'.
		 */
		unit = *str++;

		if (datepart)
		{
			switch (unit) /* before T: Y M W D */
			{
				case 'Y':
					tm->tm_year += val;
					tm->tm_mon += (fval * 12);
					break;
				case 'M':
					tm->tm_mon += val;
					AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
					break;
				case 'W':
					tm->tm_mday += val * 7;
					AdjustFractDays(fval, tm, fsec, 7);
					break;
				case 'D':
					tm->tm_mday += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
					break;
				case 'T': /* ISO 8601 4.4.3.3 Alternative Format / Basic */
				case '\0':
					if (ISO8601IntegerWidth(fieldstart) == 8 && !havefield)
					{
						tm->tm_year += val / 10000;
						tm->tm_mon  += (val / 100) % 100;
						tm->tm_mday += val % 100;
						AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
						if (unit == '\0')
							return 0;
						datepart = false;
						havefield = false;
						continue;
					}
					/* Else fall through to extended alternative format */
				case '-':		/* ISO 8601 4.4.3.3 Alternative Format,
								 * Extended */
					if (havefield)
						return DTERR_BAD_FORMAT;

					tm->tm_year += val;
					tm->tm_mon  += (fval * 12);
					if (unit == '\0')
						return 0;
					if (unit == 'T')
					{
						datepart = false;
						havefield = false;
						continue;
					}

					dterr = ParseISO8601Number(str, &str, &val, &fval);
					if (dterr)
						return dterr;
					tm->tm_mon  += val;
					AdjustFractDays(fval, tm, fsec, DAYS_PER_MONTH);
					if (*str == '\0')
						return 0;
					if (*str == 'T')
					{
						datepart = false;
						havefield = false;
						continue;
					}
					if (*str != '-')
						return DTERR_BAD_FORMAT;
					str++;
					
					dterr = ParseISO8601Number(str, &str, &val, &fval);
					if (dterr)
						return dterr;
					tm->tm_mday += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_DAY);
					if (*str == '\0')
						return 0;
					if (*str == 'T')
					{
						datepart = false;
						havefield = false;
						continue;
					}
					return DTERR_BAD_FORMAT;
				default:
					/* not a valid date unit suffix */
					return DTERR_BAD_FORMAT;
			}
		}
		else
		{
			switch (unit) /* after T: H M S */
			{
				case 'H':
					tm->tm_hour += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
					break;
				case 'M':
					tm->tm_min += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
					break;
				case 'S':
					tm->tm_sec += val;
					AdjustFractSeconds(fval, tm, fsec, 1);
					break;
				case '\0': /* ISO 8601 4.4.3.3 Alternative Format */
				    if (ISO8601IntegerWidth(fieldstart) == 6 && !havefield)
					{
						tm->tm_hour += val / 10000;
						tm->tm_min  += (val / 100) % 100;
						tm->tm_sec  += val % 100;
						AdjustFractSeconds(fval, tm, fsec, 1);
						return 0;
					}
					/* Else fall through to extended alternative format */
				case ':':		/* ISO 8601 4.4.3.3 Alternative Format,
								 * Extended */
					if (havefield)
						return DTERR_BAD_FORMAT;

					tm->tm_hour += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_HOUR);
					if (unit == '\0')
						return 0;
					
					dterr = ParseISO8601Number(str, &str, &val, &fval);
					if (dterr)
						return dterr;
					tm->tm_min  += val;
					AdjustFractSeconds(fval, tm, fsec, SECS_PER_MINUTE);
					if (*str == '\0')
						return 0;
					if (*str != ':')
						return DTERR_BAD_FORMAT;
					str++;
					
					dterr = ParseISO8601Number(str, &str, &val, &fval);
					if (dterr)
						return dterr;
					tm->tm_sec  += val;
					AdjustFractSeconds(fval, tm, fsec, 1);
					if (*str == '\0')
						return 0;
					return DTERR_BAD_FORMAT;

				default:
					/* not a valid time unit suffix */
					return DTERR_BAD_FORMAT;
			}
		}

		havefield = true;
	}

	return 0;
}


/* DecodeUnits()
 * Decode text string using lookup table.
 * This routine supports time interval decoding
 * (hence, it need not recognize timezone names).
 */
int
DecodeUnits(int field, char *lowtoken, int *val)
{
	int			type;
	const datetkn *tp;

	tp = deltacache[field];
	if (tp == NULL || strncmp(lowtoken, tp->token, TOKMAXLEN) != 0)
	{
		tp = datebsearch(lowtoken, deltatktbl, szdeltatktbl);
	}
	if (tp == NULL)
	{
		type = UNKNOWN_FIELD;
		*val = 0;
	}
	else
	{
		deltacache[field] = tp;
		type = tp->type;
		if (type == TZ || type == DTZ)
			*val = FROMVAL(tp);
		else
			*val = tp->value;
	}

	return type;
}	/* DecodeUnits() */

/*
 * Report an error detected by one of the datetime input processing routines.
 *
 * dterr is the error code, str is the original input string, datatype is
 * the name of the datatype we were trying to accept.
 *
 * Note: it might seem useless to distinguish DTERR_INTERVAL_OVERFLOW and
 * DTERR_TZDISP_OVERFLOW from DTERR_FIELD_OVERFLOW, but SQL99 mandates three
 * separate SQLSTATE codes, so ...
 */
void
DateTimeParseError(int dterr, const char *str, const char *datatype)
{
	switch (dterr)
	{
		case DTERR_FIELD_OVERFLOW:
			ereport(ERROR,
					(errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
					 errmsg("date/time field value out of range: \"%s\"",
							str),
									 errOmitLocation(true)));
			break;
		case DTERR_MD_FIELD_OVERFLOW:
			/* <nanny>same as above, but add hint about DateStyle</nanny> */
			ereport(ERROR,
					(errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
					 errmsg("date/time field value out of range: \"%s\"",
							str),
			errhint("Perhaps you need a different \"datestyle\" setting."),
					 errOmitLocation(true)));
			break;
		case DTERR_INTERVAL_OVERFLOW:
			ereport(ERROR,
					(errcode(ERRCODE_INTERVAL_FIELD_OVERFLOW),
					 errmsg("interval field value out of range: \"%s\"",
							str),
									 errOmitLocation(true)));
			break;
		case DTERR_TZDISP_OVERFLOW:
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TIME_ZONE_DISPLACEMENT_VALUE),
					 errmsg("time zone displacement out of range: \"%s\"",
							str),
									 errOmitLocation(true)));
			break;
		case DTERR_BAD_FORMAT:
		default:
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_DATETIME_FORMAT),
					 errmsg("invalid input syntax for type %s: \"%s\"",
							datatype, str),
									 errOmitLocation(true)));
			break;
	}
}

/* datebsearch()
 * Binary search -- from Knuth (6.2.1) Algorithm B.  Special case like this
 * is WAY faster than the generic bsearch().
 */
static const datetkn *
datebsearch(const char *key, const datetkn *base, int nel)
{
	const datetkn *last = base + nel - 1,
			   *position;
	int			result;

	while (last >= base)
	{
		position = base + ((last - base) >> 1);
		result = key[0] - position->token[0];
		if (result == 0)
		{
			result = strncmp(key, position->token, TOKMAXLEN);
			if (result == 0)
				return position;
		}
		if (result < 0)
			last = position - 1;
		else
			base = position + 1;
	}
	return NULL;
}

/* EncodeTimezone()
 *		Append representation of a numeric timezone offset to str.
 */
static void
EncodeTimezone(char *str, int tz, int style)
{
	int			hour,
				min,
				sec;

	sec = abs(tz);
	min = sec / SECS_PER_MINUTE;
	sec -= min * SECS_PER_MINUTE;
	hour = min / MINS_PER_HOUR;
	min -= hour * MINS_PER_HOUR;

	str += strlen(str);
	/* TZ is negated compared to sign we wish to display ... */
	*str++ = (tz <= 0 ? '+' : '-');

	if (sec != 0)
		sprintf(str, "%02d:%02d:%02d", hour, min, sec);
	else if (min != 0 || style == USE_XSD_DATES)
		sprintf(str, "%02d:%02d", hour, min);
	else
		sprintf(str, "%02d", hour);
}


/* 
 * Convenience routine for encoding dates faster than sprintf does.
 * tm is the the timestamp structure, str is the string, pos is position in
 * the string which we are at. Upon returning, it is set to the offset of the
 * last character we set in str.
 */
inline static void
fast_encode_date(struct pg_tm * tm, char *str, int *pos)
{
	/*
	 * sprintf() is very slow so we just convert the numbers to
	 * a string manually. Since we allow dates in the range
	 * 4713 BC to 5874897 AD, we have to check for years
	 * with 7, 6 and 5 digits, being careful to not add
	 * leading zeros for those. We only zero pad to four digits.
	 */
	int y = (tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1);
	
	if (y >= 1000000)
		str[(*pos)++] = y / 1000000 % 10 + '0';
	if (y >= 100000)
		str[(*pos)++] = y / 100000 % 10 + '0';
	if (y >= 10000)
		str[(*pos)++] = y / 10000 % 10 + '0';
	
	str[(*pos)++] = y/1000 % 10 + '0';
	str[(*pos)++] = y/100 % 10 + '0';
	str[(*pos)++] = y/10 % 10 + '0';
	str[(*pos)++] = y % 10 + '0';
	str[(*pos)++] = '-';
	str[(*pos)++] = tm->tm_mon/10 + '0'; 
	str[(*pos)++] = tm->tm_mon % 10 + '0';
	str[(*pos)++] = '-';
	str[(*pos)++] = tm->tm_mday/10 + '0';
	str[(*pos)++] = tm->tm_mday % 10 + '0';
	str[(*pos)] = '\0';
}

/* EncodeDateOnly()
 * Encode date as local time.
 */
void
EncodeDateOnly(struct pg_tm * tm, int style, char *str)
{
	Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

	switch (style)
	{
		case USE_ISO_DATES:
		case USE_XSD_DATES:
			/* compatible with ISO date formats */
			if (tm->tm_year > 0)
			{
				//				sprintf(str, "%04d-%02d-%02d",
				//		tm->tm_year, tm->tm_mon, tm->tm_mday);
				int j = 0;
				fast_encode_date(tm, str, &j);
			}
			else
				sprintf(str, "%04d-%02d-%02d %s",
						-(tm->tm_year - 1), tm->tm_mon, tm->tm_mday, "BC");
			break;

		case USE_SQL_DATES:
			/* compatible with Oracle/Ingres date formats */
			if (DateOrder == DATEORDER_DMY)
				sprintf(str, "%02d/%02d", tm->tm_mday, tm->tm_mon);
			else
				sprintf(str, "%02d/%02d", tm->tm_mon, tm->tm_mday);
			if (tm->tm_year > 0)
				sprintf(str + 5, "/%04d", tm->tm_year);
			else
				sprintf(str + 5, "/%04d %s", -(tm->tm_year - 1), "BC");
			break;

		case USE_GERMAN_DATES:
			/* German-style date format */
			sprintf(str, "%02d.%02d", tm->tm_mday, tm->tm_mon);
			if (tm->tm_year > 0)
				sprintf(str + 5, ".%04d", tm->tm_year);
			else
				sprintf(str + 5, ".%04d %s", -(tm->tm_year - 1), "BC");
			break;

		case USE_POSTGRES_DATES:
		default:
			/* traditional date-only style for Postgres */
			if (DateOrder == DATEORDER_DMY)
				sprintf(str, "%02d-%02d", tm->tm_mday, tm->tm_mon);
			else
				sprintf(str, "%02d-%02d", tm->tm_mon, tm->tm_mday);
			if (tm->tm_year > 0)
				sprintf(str + 5, "-%04d", tm->tm_year);
			else
				sprintf(str + 5, "-%04d %s", -(tm->tm_year - 1), "BC");
			break;
	}
}


/* EncodeTimeOnly()
 * Encode time fields only.
 */
void
EncodeTimeOnly(struct pg_tm * tm, fsec_t fsec, int *tzp, int style, char *str)
{
	str[0] = tm->tm_hour/10 + '0';
	str[1] = tm->tm_hour % 10 + '0';
	str[2] = ':';
	str[3] = tm->tm_min/10 + '0';
	str[4] = tm->tm_min % 10 + '0';
	str[5] = ':';
	str[6] = '\0';
	str += strlen(str);

	AppendSeconds(str, tm->tm_sec, fsec, MAX_TIME_PRECISION, true);

	if (tzp != NULL)
		EncodeTimezone(str, *tzp, style);
}


/* EncodeDateTime()
 * Encode date and time interpreted as local time.
 * Support several date styles:
 *	Postgres - day mon hh:mm:ss yyyy tz
 *	SQL - mm/dd/yyyy hh:mm:ss.ss tz
 *	ISO - yyyy-mm-dd hh:mm:ss+/-tz
 *	German - dd.mm.yyyy hh:mm:ss tz
 *	XSD - yyyy-mm-ddThh:mm:ss.ss+/-tz
 * Variants (affects order of month and day for Postgres and SQL styles):
 *	US - mm/dd/yyyy
 *	European - dd/mm/yyyy
 */
void
EncodeDateTime(struct pg_tm * tm, fsec_t fsec, int *tzp, char **tzn, int style, char *str)
{
	int			day;

	Assert(tm->tm_mon >= 1 && tm->tm_mon <= MONTHS_PER_YEAR);

	switch (style)
	{
		case USE_ISO_DATES:
		case USE_XSD_DATES:
			/* Compatible with ISO-8601 date formats */
			{
                int j = 0;
				/*
				 * sprintf is very slow so we just convert the numbers to
				 * a string manually. Since we allow dates in the range
				 * 4713 BC to 5874897 AD, we have to check for years
				 * with 7, 6 and 5 digits, being careful to not add
				 * leading zeros for those. We only zero pad to four digits.
				 */
				fast_encode_date(tm, str, &j);
				if (style == USE_ISO_DATES)
					str[j++] = ' ';
				else
					str[j++] = 'T';	// XSD uses a T between date and time
				
				str[j++] = tm->tm_hour/10 + '0';
				str[j++] = tm->tm_hour % 10 + '0';
				str[j++] = ':';
				str[j++] = tm->tm_min/10 + '0';
				str[j++] = tm->tm_min % 10 + '0';
				str[j++] = ':';
				str[j] = '\0';
			}

			AppendTimestampSeconds(str + strlen(str), tm, fsec);

			/*
			 * tzp == NULL indicates that we don't want *any* time zone info
			 * in the output string. *tzn != NULL indicates that we have alpha
			 * time zone info available. tm_isdst != -1 indicates that we have
			 * a valid time zone translation.
			 */
			if (tzp != NULL && tm->tm_isdst >= 0)
				EncodeTimezone(str, *tzp, style);

			if (tm->tm_year <= 0)
				sprintf(str + strlen(str), " BC");
			break;
			
		case USE_SQL_DATES:
			/* Compatible with Oracle/Ingres date formats */

			if (DateOrder == DATEORDER_DMY)
				sprintf(str, "%02d/%02d", tm->tm_mday, tm->tm_mon);
			else
				sprintf(str, "%02d/%02d", tm->tm_mon, tm->tm_mday);

			sprintf(str + 5, "/%04d %02d:%02d:",
					(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1),
					tm->tm_hour, tm->tm_min);

			AppendTimestampSeconds(str + strlen(str), tm, fsec);

			/*
			 * Note: the uses of %.*s in this function would be risky if the
			 * timezone names ever contain non-ASCII characters.  However, all
			 * TZ abbreviations in the Olson database are plain ASCII.
			 */

			if (tzp != NULL && tm->tm_isdst >= 0)
			{
				if (*tzn != NULL)
					sprintf(str + strlen(str), " %.*s", MAXTZLEN, *tzn);
				else
					EncodeTimezone(str, *tzp, style);
			}

			if (tm->tm_year <= 0)
				sprintf(str + strlen(str), " BC");
			break;

		case USE_GERMAN_DATES:
			/* German variant on European style */

			sprintf(str, "%02d.%02d", tm->tm_mday, tm->tm_mon);

			sprintf(str + 5, ".%04d %02d:%02d:",
					(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1),
					tm->tm_hour, tm->tm_min);

			AppendTimestampSeconds(str + strlen(str), tm, fsec);

			if (tzp != NULL && tm->tm_isdst >= 0)
			{
				if (*tzn != NULL)
					sprintf(str + strlen(str), " %.*s", MAXTZLEN, *tzn);
				else
					EncodeTimezone(str, *tzp, style);
			}

			if (tm->tm_year <= 0)
				sprintf(str + strlen(str), " BC");
			break;

		case USE_POSTGRES_DATES:
		default:
			/* Backward-compatible with traditional Postgres abstime dates */

			day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
			tm->tm_wday = j2day(day);

			strncpy(str, days[tm->tm_wday], 3);
			strcpy(str + 3, " ");

			if (DateOrder == DATEORDER_DMY)
				sprintf(str + 4, "%02d %3s", tm->tm_mday, months[tm->tm_mon - 1]);
			else
				sprintf(str + 4, "%3s %02d", months[tm->tm_mon - 1], tm->tm_mday);

			sprintf(str + 10, " %02d:%02d:", tm->tm_hour, tm->tm_min);

			AppendTimestampSeconds(str + strlen(str), tm, fsec);

			sprintf(str + strlen(str), " %04d",
					(tm->tm_year > 0) ? tm->tm_year : -(tm->tm_year - 1));

			if (tzp != NULL && tm->tm_isdst >= 0)
			{
				if (*tzn != NULL)
					sprintf(str + strlen(str), " %.*s", MAXTZLEN, *tzn);
				else
				{
					/*
					 * We have a time zone, but no string version. Use the
					 * numeric form, but be sure to include a leading space to
					 * avoid formatting something which would be rejected by
					 * the date/time parser later. - thomas 2001-10-19
					 */
					sprintf(str + strlen(str), " ");
					EncodeTimezone(str, *tzp, style);
				}
			}

			if (tm->tm_year <= 0)
				sprintf(str + strlen(str), " BC");
			break;
	}
}


/*
 * Helper functions to avoid duplicated code in EncodeInterval.
 */

/* Append an ISO-8601-style interval field, but only if value isn't zero */
static char *
AddISO8601IntPart(char *cp, int value, char units)
{
	if (value == 0)
		return cp;
	sprintf(cp, "%d%c", value, units);
	return cp + strlen(cp);
}

/* Append a postgres-style interval field, but only if value isn't zero */
static char *
AddPostgresIntPart(char *cp, int value, const char *units,
				   bool *is_zero, bool *is_before)
{
	if (value == 0)
		return cp;
	sprintf(cp, "%s%s%d %s%s",
			(!*is_zero) ? " " : "",
			(*is_before && value > 0) ? "+" : "",
			value,
			units,
			(value != 1) ? "s" : "");

	/*
	 * Each nonzero field sets is_before for (only) the next one.  This is a
	 * tad bizarre but it's how it worked before...
	 */
	*is_before = (value < 0);
	*is_zero = FALSE;
	return cp + strlen(cp);
}

/* Append a verbose-style interval field, but only if value isn't zero */
static char *
AddVerboseIntPart(char *cp, int value, const char *units,
				  bool *is_zero, bool *is_before)
{
	if (value == 0)
		return cp;
	/* first nonzero value sets is_before */
	if (*is_zero)
	{
		*is_before = (value < 0);
		value = abs(value);
	}
	else if (*is_before)
		value = -value;
	sprintf(cp, " %d %s%s", value, units, (value == 1) ? "" : "s");
	*is_zero = FALSE;
	return cp + strlen(cp);
}


/* EncodeInterval()
 * Interpret time structure as a delta time and convert to string.
 *
 * Support "traditional Postgres" and ISO-8601 styles.
 * Actually, afaik ISO does not address time interval formatting,
 *	but this looks similar to the spec for absolute date/time.
 * - thomas 1998-04-30
 *
 * Actually, afaik, ISO 8601 does specify formats for "time
 * intervals...[of the]...format with time-unit designators", which
 * are pretty ugly.  The format looks something like
 *     P1Y1M1DT1H1M1.12345S
 * but useful for exchanging data with computers instead of humans.
 * - ron 2003-07-14
 *
 * And ISO's SQL 2008 standard specifies standards for
 * "year-month literal"s (that look like '2-3') and
 * "day-time literal"s (that look like ('4 5:6:7')
 */
void
EncodeInterval(struct pg_tm * tm, fsec_t fsec, int style, char *str)
{
	char	   *cp = str;
		int			year = tm->tm_year;
		int			mon  = tm->tm_mon;
		int			mday = tm->tm_mday;
		int			hour = tm->tm_hour;
		int			min  = tm->tm_min;
		int			sec  = tm->tm_sec;
		bool		is_before = FALSE;
		bool		is_zero = TRUE;

	/*
	 * The sign of year and month are guaranteed to match, since they are
	 * stored internally as "month". But we'll need to check for is_before and
	 * is_zero when determining the signs of day and hour/minute/seconds
	 * fields.
	 */
	switch (style)
	{
	/* SQL Standard interval format */
	case INTSTYLE_SQL_STANDARD:
		{
			bool has_negative = year < 0 || mon  < 0 ||
								mday < 0 || hour < 0 ||
								min  < 0 || sec  < 0 || fsec < 0;
			bool has_positive = year > 0 || mon  > 0 ||
								mday > 0 || hour > 0 ||
								min  > 0 || sec  > 0 || fsec > 0;
			bool has_year_month = year != 0 || mon  != 0;
			bool has_day_time   = mday != 0 || hour != 0 ||
								  min  != 0 || sec  != 0 || fsec != 0;
			bool has_day        = mday != 0;
			bool sql_standard_value = !(has_negative && has_positive) &&
									  !(has_year_month && has_day_time);

			/*
			 * SQL Standard wants only 1 "<sign>" preceding the whole
			 * interval ... but can't do that if mixed signs.
			 */
			if (has_negative && sql_standard_value)
			{
				*cp++ = '-';
				year = -year;
				mon  = -mon;
				mday = -mday;
				hour = -hour;
				min  = -min;
				sec  = -sec;
				fsec = -fsec;
			}

			if (!has_negative && !has_positive)
			{
				sprintf(cp, "0");
			}
			else if (!sql_standard_value)
			{
				/*
					 * For non sql-standard interval values, force outputting
					 * the signs to avoid ambiguities with intervals with
					 * mixed sign components.
				 */
				char year_sign = (year < 0 || mon < 0) ? '-' : '+';
				char day_sign = (mday < 0) ? '-' : '+';
				char sec_sign = (hour < 0 || min < 0 ||
								 sec < 0 || fsec < 0) ? '-' : '+';

				sprintf(cp, "%c%d-%d %c%d %c%d:%02d:",
						year_sign, abs(year), abs(mon),
						day_sign, abs(mday),
						sec_sign, abs(hour), abs(min));
				cp += strlen(cp);
				AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
			}
			else if (has_year_month)
			{
				sprintf(cp, "%d-%d", year, mon);
			}
			else if (has_day)
			{
				sprintf(cp, "%d %d:%02d:", mday, hour, min);
				cp += strlen(cp);
				AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
			}
			else
			{
				sprintf(cp, "%d:%02d:", hour, min);
				cp += strlen(cp);
				AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
			}
		}
		break;

	/* ISO 8601 "time-intervals by duration only" */
	case INTSTYLE_ISO_8601:
		/* special-case zero to avoid printing nothing */
		if (year == 0 && mon == 0 && mday == 0 &&
		    hour == 0 && min == 0 && sec  == 0 && fsec == 0)
		{
			sprintf(cp, "PT0S");
			break;
		}
		*cp++ = 'P';
		cp = AddISO8601IntPart(cp, year, 'Y');
		cp = AddISO8601IntPart(cp, mon , 'M');
		cp = AddISO8601IntPart(cp, mday, 'D');
		if (hour != 0 || min != 0 || sec != 0 || fsec != 0)
			*cp++ = 'T';
		cp = AddISO8601IntPart(cp, hour, 'H');
		cp = AddISO8601IntPart(cp, min , 'M');
		if (sec != 0 || fsec != 0)
		{
			if (sec < 0 || fsec < 0)
				*cp++ = '-';
			AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
			cp += strlen(cp);
			*cp++ = 'S';
			*cp++ = '\0';
		}
		break;

	/* Compatible with postgresql < 8.4 when DateStyle = 'iso' */
	case INTSTYLE_POSTGRES:
		cp = AddPostgresIntPart(cp, year, "year", &is_zero, &is_before);
		cp = AddPostgresIntPart(cp, mon, "mon", &is_zero, &is_before);
		cp = AddPostgresIntPart(cp, mday, "day", &is_zero, &is_before);
		if (is_zero || hour != 0 || min != 0 || sec != 0 || fsec != 0)
		{
			bool	minus = (hour < 0 || min < 0 || sec < 0 || fsec < 0);

			sprintf(cp, "%s%s%02d:%02d:",
					is_zero ? "" : " ",
					(minus ? "-" : (is_before ? "+" : "")),
					abs(hour), abs(min));
			cp += strlen(cp);
			AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, true);
		}
		break;

	/* Compatible with postgresql < 8.4 when DateStyle != 'iso' */
	case INTSTYLE_POSTGRES_VERBOSE:
	default:
		strcpy(cp, "@");
		cp++;
		cp = AddVerboseIntPart(cp, year, "year", &is_zero, &is_before);
		cp = AddVerboseIntPart(cp, mon, "mon", &is_zero, &is_before);
		cp = AddVerboseIntPart(cp, mday, "day", &is_zero, &is_before);
		cp = AddVerboseIntPart(cp, hour, "hour", &is_zero, &is_before);
		cp = AddVerboseIntPart(cp, min, "min", &is_zero, &is_before);
		if (sec != 0 || fsec != 0)
		{
			*cp++ = ' ';
			if (sec < 0 || (sec == 0 && fsec < 0))
			{
				if (is_zero)
					is_before = TRUE;
				else if (!is_before)
					*cp++ = '-';
			}
			else if (is_before)
				*cp++ = '-';
			AppendSeconds(cp, sec, fsec, MAX_INTERVAL_PRECISION, false);
			cp += strlen(cp);
			sprintf(cp, " sec%s",
					(abs(sec) != 1 || fsec != 0) ? "s" : "");
			is_zero = FALSE;
		}
		/* identically zero? then put in a unitless zero... */
		if (is_zero)
			strcat(cp, " 0");
		if (is_before)
			strcat(cp, " ago");
		break;
	}
}


/*
 * We've been burnt by stupid errors in the ordering of the datetkn tables
 * once too often.	Arrange to check them during postmaster start.
 */
static bool
CheckDateTokenTable(const char *tablename, const datetkn *base, int nel)
{
	bool		ok = true;
	int			i;

	for (i = 1; i < nel; i++)
	{
		if (strncmp(base[i - 1].token, base[i].token, TOKMAXLEN) >= 0)
		{
			/* %.*s is safe since all our tokens are ASCII */
			elog(LOG, "ordering error in %s table: \"%.*s\" >= \"%.*s\"",
				 tablename,
				 TOKMAXLEN, base[i - 1].token,
				 TOKMAXLEN, base[i].token);
			ok = false;
		}
	}
	return ok;
}

bool
CheckDateTokenTables(void)
{
	bool		ok = true;

	Assert(UNIX_EPOCH_JDATE == date2j(1970, 1, 1));
	Assert(POSTGRES_EPOCH_JDATE == date2j(2000, 1, 1));

	ok &= CheckDateTokenTable("datetktbl", datetktbl, szdatetktbl);
	ok &= CheckDateTokenTable("deltatktbl", deltatktbl, szdeltatktbl);
	return ok;
}

/*
 * This function gets called during timezone config file load or reload
 * to create the final array of timezone tokens.  The argument array
 * is already sorted in name order.  This data is in a temporary memory
 * context and must be copied to somewhere permanent.
 */
void
InstallTimeZoneAbbrevs(tzEntry *abbrevs, int n)
{
	datetkn    *newtbl;
	int			i;

	/*
	 * Copy the data into TopMemoryContext and convert to datetkn format.
	 */
	newtbl = (datetkn *) MemoryContextAlloc(TopMemoryContext,
											n * sizeof(datetkn));
	for (i = 0; i < n; i++)
	{
		/* do NOT use strlcpy here; token field need not be null-terminated */
		strncpy(newtbl[i].token, abbrevs[i].abbrev, TOKMAXLEN);
		newtbl[i].type = abbrevs[i].is_dst ? DTZ : TZ;
		TOVAL(&newtbl[i], abbrevs[i].offset / 60);
	}

	/* Check the ordering, if testing */
	Assert(CheckDateTokenTable("timezone offset", newtbl, n));

	/* Now safe to replace existing table (if any) */
	if (timezonetktbl)
		pfree(timezonetktbl);
	timezonetktbl = newtbl;
	sztimezonetktbl = n;

	/* clear date cache in case it contains any stale timezone names */
	for (i = 0; i < MAXDATEFIELDS; i++)
		datecache[i] = NULL;
}

/*
 * This set-returning function reads all the available time zone abbreviations
 * and returns a set of (abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_abbrevs(PG_FUNCTION_ARGS)
{
	FuncCallContext *funcctx;
	int		   *pindex;
	Datum		result;
	HeapTuple	tuple;
	Datum		values[3];
	bool		nulls[3];
	char		buffer[TOKMAXLEN + 1];
	unsigned char *p;
	struct pg_tm tm;
	Interval   *resInterval;

	/* stuff done only on the first call of the function */
	if (SRF_IS_FIRSTCALL())
	{
		TupleDesc	tupdesc;
		MemoryContext oldcontext;

		/* create a function context for cross-call persistence */
		funcctx = SRF_FIRSTCALL_INIT();

		/*
		 * switch to memory context appropriate for multiple function calls
		 */
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		/* allocate memory for user context */
		pindex = (int *) palloc(sizeof(int));
		*pindex = 0;
		funcctx->user_fctx = (void *) pindex;

		/*
		 * build tupdesc for result tuples. This must match this function's
		 * pg_proc entry!
		 */
		tupdesc = CreateTemplateTupleDesc(3, false);
		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "abbrev",
						   TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "utc_offset",
						   INTERVALOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_dst",
						   BOOLOID, -1, 0);

		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
		MemoryContextSwitchTo(oldcontext);
	}

	/* stuff done on every call of the function */
	funcctx = SRF_PERCALL_SETUP();
	pindex = (int *) funcctx->user_fctx;

	if (*pindex >= sztimezonetktbl)
		SRF_RETURN_DONE(funcctx);

	MemSet(nulls, 0, sizeof(nulls));

	/*
	 * Convert name to text, using upcasing conversion that is the inverse of
	 * what ParseDateTime() uses.
	 */
	strncpy(buffer, timezonetktbl[*pindex].token, TOKMAXLEN);
	buffer[TOKMAXLEN] = '\0';	/* may not be null-terminated */
	for (p = (unsigned char *) buffer; *p; p++)
		*p = pg_toupper(*p);

	values[0] = CStringGetTextDatum(buffer);

	MemSet(&tm, 0, sizeof(struct pg_tm));
	tm.tm_min = (-1) * FROMVAL(&timezonetktbl[*pindex]);
	resInterval = (Interval *) palloc(sizeof(Interval));
	tm2interval(&tm, 0, resInterval);
	values[1] = IntervalPGetDatum(resInterval);

	Assert(timezonetktbl[*pindex].type == DTZ ||
		   timezonetktbl[*pindex].type == TZ);
	values[2] = BoolGetDatum(timezonetktbl[*pindex].type == DTZ);

	(*pindex)++;

	tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
	result = HeapTupleGetDatum(tuple);

	SRF_RETURN_NEXT(funcctx, result);
}

/*
 * This set-returning function reads all the available full time zones
 * and returns a set of (name, abbrev, utc_offset, is_dst).
 */
Datum
pg_timezone_names(PG_FUNCTION_ARGS)
{
	MemoryContext oldcontext;
	FuncCallContext *funcctx;
	pg_tzenum  *tzenum;
	pg_tz	   *tz;
	Datum		result;
	HeapTuple	tuple;
	Datum		values[4];
	bool		nulls[4];
	int			tzoff;
	struct pg_tm tm;
	fsec_t		fsec;
	char	   *tzn;
	Interval   *resInterval;
	struct pg_tm itm;

	/* stuff done only on the first call of the function */
	if (SRF_IS_FIRSTCALL())
	{
		TupleDesc	tupdesc;

		/* create a function context for cross-call persistence */
		funcctx = SRF_FIRSTCALL_INIT();

		/*
		 * switch to memory context appropriate for multiple function calls
		 */
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		/* initialize timezone scanning code */
		tzenum = pg_tzenumerate_start();
		funcctx->user_fctx = (void *) tzenum;

		/*
		 * build tupdesc for result tuples. This must match this function's
		 * pg_proc entry!
		 */
		tupdesc = CreateTemplateTupleDesc(4, false);
		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
						   TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "abbrev",
						   TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "utc_offset",
						   INTERVALOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_dst",
						   BOOLOID, -1, 0);

		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
		MemoryContextSwitchTo(oldcontext);
	}

	/* stuff done on every call of the function */
	funcctx = SRF_PERCALL_SETUP();
	tzenum = (pg_tzenum *) funcctx->user_fctx;

	/* search for another zone to display */
	for (;;)
	{
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
		tz = pg_tzenumerate_next(tzenum);
		MemoryContextSwitchTo(oldcontext);

		if (!tz)
		{
			pg_tzenumerate_end(tzenum);
			funcctx->user_fctx = NULL;
			SRF_RETURN_DONE(funcctx);
		}

		/* Convert now() to local time in this zone */
		if (timestamp2tm(GetCurrentTransactionStartTimestamp(),
						 &tzoff, &tm, &fsec, &tzn, tz) != 0)
			continue;			/* ignore if conversion fails */

		/* Ignore zic's rather silly "Factory" time zone */
		if (tzn && strcmp(tzn, "Local time zone must be set--see zic manual page") == 0)
			continue;

		/* Found a displayable zone */
		break;
	}

	MemSet(nulls, 0, sizeof(nulls));

	values[0] = CStringGetTextDatum(pg_get_timezone_name(tz));
	values[1] = CStringGetTextDatum(tzn ? tzn : "");

	MemSet(&itm, 0, sizeof(struct pg_tm));
	itm.tm_sec = -tzoff;
	resInterval = (Interval *) palloc(sizeof(Interval));
	tm2interval(&itm, 0, resInterval);
	values[2] = IntervalPGetDatum(resInterval);

	values[3] = BoolGetDatum(tm.tm_isdst > 0);

	tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
	result = HeapTupleGetDatum(tuple);

	SRF_RETURN_NEXT(funcctx, result);
}