[tz] Fwd: [IANA #636310] how to check a time

[Guy Harris]

On Nov 28, 2012, at 5:28 PM, Gemma Conn <gemma at biozone.co.nz> wrote:

> Hello,
> 
> Can you point me in the direction of where I can double check that IANA has the correct time for New Zealand?

Go to

	http://www.iana.org/time-zones

download the latest version of the time zone data (and possibly download the latest version of the time zone code and read the zic.8.txt file for a description of the time zone data file), and then check what the time zone data file "australasia" says about New Zealand.

What tzdata2012j's australasia file says is:

###############################################################################

# New Zealand

# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
Rule	NZ	1927	only	-	Nov	 6	2:00	1:00	S
Rule	NZ	1928	only	-	Mar	 4	2:00	0	M
Rule	NZ	1928	1933	-	Oct	Sun>=8	2:00	0:30	S
Rule	NZ	1929	1933	-	Mar	Sun>=15	2:00	0	M
Rule	NZ	1934	1940	-	Apr	lastSun	2:00	0	M
Rule	NZ	1934	1940	-	Sep	lastSun	2:00	0:30	S
Rule	NZ	1946	only	-	Jan	 1	0:00	0	S
# Since 1957 Chatham has been 45 minutes ahead of NZ, but there's no
# convenient notation for this so we must duplicate the Rule lines.
Rule	NZ	1974	only	-	Nov	Sun>=1	2:00s	1:00	D
Rule	Chatham	1974	only	-	Nov	Sun>=1	2:45s	1:00	D
Rule	NZ	1975	only	-	Feb	lastSun	2:00s	0	S
Rule	Chatham	1975	only	-	Feb	lastSun	2:45s	0	S
Rule	NZ	1975	1988	-	Oct	lastSun	2:00s	1:00	D
Rule	Chatham	1975	1988	-	Oct	lastSun	2:45s	1:00	D
Rule	NZ	1976	1989	-	Mar	Sun>=1	2:00s	0	S
Rule	Chatham	1976	1989	-	Mar	Sun>=1	2:45s	0	S
Rule	NZ	1989	only	-	Oct	Sun>=8	2:00s	1:00	D
Rule	Chatham	1989	only	-	Oct	Sun>=8	2:45s	1:00	D
Rule	NZ	1990	2006	-	Oct	Sun>=1	2:00s	1:00	D
Rule	Chatham	1990	2006	-	Oct	Sun>=1	2:45s	1:00	D
Rule	NZ	1990	2007	-	Mar	Sun>=15	2:00s	0	S
Rule	Chatham	1990	2007	-	Mar	Sun>=15	2:45s	0	S
Rule	NZ	2007	max	-	Sep	lastSun	2:00s	1:00	D
Rule	Chatham	2007	max	-	Sep	lastSun	2:45s	1:00	D
Rule	NZ	2008	max	-	Apr	Sun>=1	2:00s	0	S
Rule	Chatham	2008	max	-	Apr	Sun>=1	2:45s	0	S
# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
Zone Pacific/Auckland	11:39:04 -	LMT	1868 Nov  2
			11:30	NZ	NZ%sT	1946 Jan  1
			12:00	NZ	NZ%sT
Zone Pacific/Chatham	12:13:48 -	LMT	1957 Jan  1
			12:45	Chatham	CHA%sT


# Auckland Is
# uninhabited; Maori and Moriori, colonial settlers, pastoralists, sealers,
# and scientific personnel have wintered

# Campbell I
# minor whaling stations operated 1909/1914
# scientific station operated 1941/1995;
# previously whalers, sealers, pastoralists, and scientific personnel wintered
# was probably like Pacific/Auckland

###############################################################################

> I am worried that IANA has the wrong time for New Zealand, as Google Calendar which claims to use IANA Time Zone Database, displays the incorrect time for New Zealand. It displays GMT + 12 Auckland but it should be GMT + 13 Auckland, as we are observing Daylight Savings time.

The rules that apply currently are:

Rule	NZ	2007	max	-	Sep	lastSun	2:00s	1:00	D

and

Rule	NZ	2008	max	-	Apr	Sun>=1	2:00s	0	S

which say that Daylight Savings Time starts on the last Sunday in September at 2:00 standard time, shifting by one hour, and ends on the first Sunday in April at 2:00 standard time (3:00 DST).

If the calendar is correctly set to honor the New Zealand DST rules, this would seem to indicate that either

	1) whatever Google Calendar is using isn't the IANA time zone database

or

	2) they're not using it correctly

or

	3) they think the last Sunday in September 2012 hasn't happened yet.