Change in Mongolian daylight saving time

Paul Eggert eggert at
Sat Apr 17 05:20:31 UTC 2004

At Sat, 17 Apr 2004 11:30:25 +0900, Ganbold <ganbold at> writes:

> Last time the rule was changed in 2001 only.

Thanks for the clarification.

The current tz data for Mongolia in 2001 relies on this comment:

# From Rives McDow (2001-05-13):
# In addition to Mongolia starting daylight savings as reported earlier
# (adopted DST on 2001-04-27 02:00 local time, ending 2001-09-28),

This conflicts with the rules that you mentioned, in two ways.

First, according to McDow the 2001 daylight-saving began on April 27,
which was a Friday, not a Saturday; and daylight-saving ended on
the last Friday in September, not the last Saturday.

It's possible that McDow's informant got confused about Friday versus
Saturday; it wouldn't be the first time that this has happened.  But
the part about the end of April sounds plausible -- it's quite common
for countries to start daylight-saving late their first year.  So,
unless you disagree, I'm inclined to change the rules to be the

Rule	Mongol	2001	only	-	Apr	lastSat	2:00	1:00	S
Rule	Mongol	2001	max	-	Sep	lastSat	2:00	0	-
Rule	Mongol	2002	max	-	Mar	lastSat	2:00	1:00	S

i.e., from the last Saturday in March at 02:00 to the last Saturday in
September in 02:00, except that in 2001 it didn't start until the last
Saturday in April.

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