Change in Mongolian daylight saving time
Hello, Current rule settings for Mongolia in /usr/src/share/zoneinfo/asia is wrong. It should be changed from: ... Rule Mongol 2001 only - Apr 27 2:00s 1:00 S Rule Mongol 2001 only - Sep 28 2:00s 0 - ... To the following: ... Rule Mongol 2001 only - Mar lastSat 2:00s 1:00 S Rule Mongol 2001 only - Sep lastSat 2:00s 0 - ... Daylight saving occurs at 02:00 local time last Saturday of March. It will changes back to normal at 02:00 local time last Saturday of September. Please make appropriate changes. Please let me know if you have any questions. sincerely, Ganbold Ts. Mongolia
At Fri, 16 Apr 2004 16:36:02 +0900, Ganbold <ganbold@micom.mng.net> writes:
Daylight saving occurs at 02:00 local time last Saturday of March. It will changes back to normal at 02:00 local time last Saturday of September. Please make appropriate changes.
Thanks for the news. Can you please let me know when the rules changed? The current zoneinfo tables say that Mongolia observed daylight-saving time from 1983 through 1998. Then it stopped (except that it observed daylight-saving time once, in 2001). Is this information correct? If so, then we'll assume that Mongolia changed the rules again, and started observing daylight-saving again this year. Do you think they will change the rules again soon? Thanks.
Hi Paul, Thank you for your reply. At 04:46 AM 17.04.2004, you wrote:
At Fri, 16 Apr 2004 16:36:02 +0900, Ganbold <ganbold@micom.mng.net> writes:
Daylight saving occurs at 02:00 local time last Saturday of March. It will changes back to normal at 02:00 local time last Saturday of September. Please make appropriate changes.
Thanks for the news. Can you please let me know when the rules changed?
As I remember this rule was changed in 2001.
The current zoneinfo tables say that Mongolia observed daylight-saving time from 1983 through 1998. Then it stopped (except that it observed daylight-saving time once, in 2001). Is this information correct?
Yes it is correct. However Mongolia is continuing to observe daylight saving time since 2001.
If so, then we'll assume that Mongolia changed the rules again, and started observing daylight-saving again this year. Do you think they will change the rules again soon?
Last time the rule was changed in 2001 only. I don't know really when they will change again the rule. At least I know they will continue it this year, since time is already changed. Please let me know if you have further questions. thank you, Ganbold Micom Co. Ulaanbaatar, Mongolia
Thanks.
At Sat, 17 Apr 2004 11:30:25 +0900, Ganbold <ganbold@micom.mng.net> 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 following: 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.
Hi Paul, At 02:20 PM 17.04.2004, you wrote:
At Sat, 17 Apr 2004 11:30:25 +0900, Ganbold <ganbold@micom.mng.net> 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.
Yes, I agree.
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.
I don't remember when daylight savings started in 2001. Probably it was on April 27. Maybe McDow is confused about the day. Usually daylight saving started last Saturday 2:00AM by local Mongolian time. It means 6:00PM by GMT/UTC Friday.
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.
OK.
So, unless you disagree, I'm inclined to change the rules to be the following:
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.
I agree with it. 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. That's why I started looking at /usr/src/share/zoneinfo/asia file and found out wrong rules for Mongolia. Can you give me some advice and solution to make time synchronization which counts daylight saving? thanks in advance, Ganbold
At Sat, 17 Apr 2004 16:15:51 +0900, Ganbold <ganbold@micom.mng.net> 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 <http://www.twinsun.com/tz/tz-link.htm>. 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) "/usr/share/lib/zoneinfo/Asia/Ulaanbaatar". 4. Set your TZ environment variable to "Asia/Ulaanbaatar".
participants (2)
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Ganbold -
Paul Eggert