Redesign start end time when absent and present
diff --git a/commands/interceptor/duration.go b/commands/interceptor/duration.go
index 1be9974..88468ec 100644
--- a/commands/interceptor/duration.go
+++ b/commands/interceptor/duration.go
@@ -96,7 +96,7 @@
 	if len(start) > 0 && len(end) > 0 {
 		start, end = AlignPrecision(start, end)
 
-		if step, startTime, err = tryParseTime(start); err != nil {
+		if _, startTime, err = tryParseTime(start); err != nil {
 			logger.Log.Fatalln("Unsupported time format:", start, err)
 		}
 		if step, endTime, err = tryParseTime(end); err != nil {