
Can anyone please shed any light on why R DateTimeClasses give weird times for when daylight saving time information changes, and which aren't consistent with the OS?

Example:

	Expected result: in New Zealand DST stopped (NZDT -> NZST) at 03:00 NZDT on 2010-04-04, as confirmed by the OS time zone info (OS X 10.8.2):

	zdump -v /etc/localtime
		/etc/localtime  Sat Apr  3 13:59:59 2010 UTC = Sun Apr  4 02:59:59 2010 NZDT isdst=1
		/etc/localtime  Sat Apr  3 14:00:00 2010 UTC = Sun Apr  4 02:00:00 2010 NZST isdst=0

	Result in R: R has DST changing at 02:26:08, instead of 03:00!

	> a<-as.POSIXlt('2010-04-04 02:26:07',tz="NZ")
	> a$isdst
	[1] 1
	> b<-as.POSIXlt('2010-04-04 02:26:08',tz="NZ")
	> b$isdst
	[1] 0


So does R get its DST information from somewhere else? Any suggestions would be much appreciated!

Thanks

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