Use os:timestamp over locky erlang:now
diff --git a/src/folsom_metrics_duration.erl b/src/folsom_metrics_duration.erl
index 6b53566..da937f0 100644
--- a/src/folsom_metrics_duration.erl
+++ b/src/folsom_metrics_duration.erl
@@ -45,10 +45,10 @@
     ets:insert(?DURATION_TABLE, Dur).
 
 update(Name, timer_start) ->
-    StartTime = erlang:now(),
+    StartTime = os:timestamp(),
     ets:update_element(?DURATION_TABLE, Name, {3, StartTime});
 update(Name, timer_end) ->
-    EndTime = erlang:now(),
+    EndTime = os:timestamp(),
     case ets:lookup_element(?DURATION_TABLE, Name, 3) of
         undefined ->
             ok;
diff --git a/src/folsom_utils.erl b/src/folsom_utils.erl
index d6192cd..8b63ba3 100644
--- a/src/folsom_utils.erl
+++ b/src/folsom_utils.erl
@@ -41,11 +41,11 @@
     [to_atom(Tag) || Tag <- Tags].
 
 now_epoch() ->
-    {Mega, Sec, _} = erlang:now(),
+    {Mega, Sec, _} = os:timestamp(),
     (Mega * 1000000 + Sec).
 
 now_epoch_micro() ->
-    {Mega, Sec, Micro} = erlang:now(),
+    {Mega, Sec, Micro} = os:timestamp(),
     (Mega * 1000000 + Sec) * 1000000 + Micro.
 
 get_ets_size(Tab) ->