Change in Mongolian daylight saving time

Paul Eggert eggert at
Sat Apr 17 09:29:58 UTC 2004

At Sat, 17 Apr 2004 16:15:51 +0900, Ganbold <ganbold at> writes:

> One more question, maybe this is off topic. How to make time
> synchronization? I installed ntp daemon which makes synchronization
> from some public time servers. However because of daylight saving
> time it is still off by 1 hour.

Most likely, NTP is working correctly; it is merely your zoneinfo
data that are wrong.

You can test this by using the command "date -u".  If "date -u" prints
the correct Universal time, then it's not an NTP problem; it's a
zoneinfo problem.

> Can you give me some advice and solution to make time
> synchronization which counts daylight saving?

Assuming NTP is not the problem, here's what I'd do:

1.  Obtain the latest zoneinfo data as described in

2.  Make the following change to the "asia" file.

-Rule	Mongol	2001	only	-	Apr	27	2:00s	1:00	S
-Rule	Mongol	2001	only	-	Sep	28	2:00s	0	-
+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

3.  Run the command "zic asia".  You may also need to give a -d option
    to "zic", to match the location of your local configuration.
    This should create a file whose name is (say)

4.  Set your TZ environment variable to "Asia/Ulaanbaatar".

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