Chile DST history

Sun Oct 8 04:45:38 UTC 2006

The page http://www.worldtimeserver.com claims that Chile starts DST this
Sunday 8.th. of October at 1:00 so I got interested in if we have the
information right concerning Chile. This made me revise the information in
the tz database, which lead to the page http://www.shoa.cl which represents
the oficial timekeeping of the armed forces of Chile, which in turn is the
only authority on time setting matters in Chile since 11.th. of January 1966
according to decree No. 25 of that year.

CIA factbook says on page
http://www.cia.gov/cia/publications/factbook/geos/ci.html
that DST starts second Sunday in October, ends Second Sunday of March. But
according to the official page it is really Second Saturday of October at
24:00 and Second Saturday of March at 24:00. 2006 happens to be a year where
these two rules get to different results, in fact DST begins in Chile in
2006 Saturday 14.th. of March at 24:00, according to one of the Chile web
pages.

In tz database, file southamerica says:
# From Paul Eggert (2002-10-24):
# <http://www.shoa.cl/shoa/faqhoraoficial.htm> gives many details that
# disagree with the following table, but we haven't had time to compare
them.

As far as I see it, this is the maximum authority of time setting in Chile,
which should supersede tz database, Shanks, IATA etc. If you disagree on
this point, please forward good arguments. Therefore I recommend the
following changes to the tz database.

I took the time to check out in detail what the differences are from this
source compared to tz database, based on the page 
http://www.horaoficial.cl/horaof.htm which contains timezone and time
history in Chile since 1884. Here are the results if you apply those to the
tz database (I might have made mistakes, since there are plenty of
differences):

# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE
LETTER/S
Rule	Chile	1927	1931	-	Sep	 1	0:00	1:00	S
Rule	Chile	1928	1932	-	Apr	 1	0:00	0	-
Rule	Chile	1946	only	-	Aug	27	4:00u	1:00	S
Rule	Chile	1947	only	-	May	21	2:00u	0	-
Rule	Chile	1968	only	-	Nov	 2	4:00u	1:00	S
Rule	Chile	1969	only	-	Mar	29	3:00u	0	-
Rule	Chile	1969	only	-	Nov	22	4:00u	1:00	S
Rule	Chile	1970	only	-	Mar	28	3:00u	0	-
Rule	Chile	1971	only	-	Mar	13	3:00u	0	-
Rule	Chile	1970	1972	-	Oct	Sun>=9	4:00u	1:00	S
Rule	Chile	1973	only	-	Sep	29	4:00u	1:00	S
Rule	Chile	1972	1986	-	Mar	Sun>=9	3:00u	0	-
Rule	Chile	1974	1987	-	Oct	Sun>=9	4:00u	1:00	S
Rule	Chile	1987	only	-	Apr	12	3:00u	0	-
Rule	Chile	1988	only	-	Oct	Sun>=1	4:00u	1:00	S
Rule	Chile	1988	1989	-	Mar	Sun>=9	3:00u	0	-
Rule	Chile	1989	only	-	Oct	Sun>=9	4:00u	1:00	S
Rule	Chile	1990	only	-	Mar	18	3:00u	0	-
Rule	Chile	1990	only	-	Sep	16	4:00u	1:00	S
Rule	Chile	1991	1996	-	Mar	Sun>=9	3:00u	0	-
Rule	Chile	1991	1997	-	Oct	Sun>=9	4:00u	1:00	S
Rule	Chile	1997	only	-	Mar	30	3:00u	0	-
Rule	Chile	1998	only	-	Sep	27	4:00u	1:00	S
Rule	Chile	1998	only	-	Mar	Sun>=9	3:00u	0	-
Rule	Chile	1999	only	-	Apr	 4	3:00u	0	-
Rule	Chile	1999	max	-	Oct	Sun>=9	4:00u	1:00	S
Rule	Chile	2000	max	-	Mar	Sun>=9	3:00u	0	-
# IATA SSIM anomalies: (1992-02) says 1992-03-14;
# (1996-09) says 1998-03-08.  Ignore these.
# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
Zone America/Santiago	-4:42:40 -	LMT	1890
			-4:42:40 -	SMT	1910 Jan 10	    #
Santiago Mean Time
			-5:00	-	CL%sT	1916 Jul  1    # Chile Time
			-4:42:46 -	SMT	1918 Sep 10	    #
Santiago Mean Time				-4:00	-	CL%sT	1919
Jul  1    # Chile Time
			-4:42:46 -	SMT	1927 Aug 22	    #
Santiago Mean Time				-5:00	Chile	CL%sT	1932
Sep    # Chile Time
			-4:00	Chile	CL%sT
Zone Pacific/Easter	-7:17:28 -	LMT	1890	    # Mataveri
			-7:17:28 -	MMT	1932 Sep    # Mataveri Mean
Time
			-7:00	Chile	EAS%sT	1982 Jan 18 21:00 # Easter I
Time
			-6:00	Chile	EAS%sT

Note (1)
Since the starting and ending of DST in 1927-1932 is a bit confusing (not
covered by a decree of when it ended), I used the tz database as it was,
since the first two transitions concur with the web page. It seems that the
Chile web page claims that it stopped in 1928, but it doesn't mention a
decree about that.

Note (2)
The DST employment in 1946-1947 was decreed only for the central zone
(whatever that is, but surely including Santiago), not for the rest of the
country. But since this happens before our cutoff date of 1970, there is no
need to make an extra timezone.

Note (3)
Since one of the IATA anomalies were agreeing with the Chile page, I deleted
that from the commentary. I also did not put commentary for if the above
changes are accepted (like "Jesper Norgaard wrote ..."), I will leave that
happily to whoever might implement it in a coming version of the tz
database.

Regards,
- Jesper

Jesper Nørgaard Welen
Email: jnorgard at Prodigy.Net.mx	
Project Leader (Líder de Proyecto) Software
CIMMYT  -  Centro Internacional de Mejoramiento de Maíz y Trigo
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