[tz] Are these valid timezone definitions?

Zefram zefram at fysh.org
Wed Jun 6 21:18:00 UTC 2012

david singleton wrote:
>Is this a known problem?  Or a problem with how the timezones are defined?

I think you're confusing yourself by the way you're setting the time.
It's always difficult to test timezone offset issues when you're
stating the test times in local time.  By the way, your testing method
of modifying the system clock is problematic.  It's much better to use
the -d option of GNU date to display a particular time without touching
the clock.

Looking at DST ending with the zone you describe, I get:

	$ export TZ="NZST-12:00:00NZDT-13:00:00,M10.1.0,M3.3.0"
	$ date -d '2012-03-17 12:55 Z' +'%F %T %z %Z %s'
	2012-03-18 01:55:00 +1300 NZDT 1331988900
	$ date -d '2012-03-17 13:05 Z' +'%F %T %z %Z %s'
	2012-03-18 01:05:00 +1200 NZST 1331989500

This looks perfectly correct to me.  I've specified (in UT, that's the
"Z") times that are ten minutes apart.  The final number in the output
(%s) is (except for leap seconds) a linear count of seconds, and you can
see it's increased by 600, confirming that these times really are exactly
ten minutes apart.  The times span the end of DST, and they show that the
NZ local clock (%T) jumped back an hour.  The jump is explained by the UT
offset (%z) having reduced by an hour, and you can see the abbreviation
(%Z) has also changed accordingly.


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