On 2023-09-19 01:00, fr via tz wrote:
The Government of Mongolia is planning to switch to the regular summer time from 22-26 March, 2024. Currently, the discussions are made within the Government as well as at the Parliament. We expect that final decision will be made in the October. Therefore, is it possible to arrange the switching process in the next 5 months? Is there any extraordinary cases like us or not? Or shall we make our changes in the September 2024?
Thank you for letting us know. If the Mongolian government publishes its official decision in October and notifies us, we can generate a new TZDB release quickly. However, it will take some months for this release to trickle out to cell phones, computers, and other devices, because many intermediaries check TZDB data before redistributing it, and because users often wait for some time before installing updates. This is why we suggest a year's notice for changes. (Even a year's notice is not perfect, as some devices will never be updated, but one cannot wait forever.) With five months' notice many devices will be updated, but it is hard to predict how many. So it is a judgment call as to whether five months is enough for Mongolia. Although the TZDB project suggests twelve months' notice, this is not a strict requirement. Although it is not clear from your email, I guess that the government of Mongolia plans to switch its time zone permanently, so that clocks in Ulaanbaatar would move forward one hour on (say) March 29, 2025 at 02:00 local time, and that no further clock adjustments would occur afterwards. That is, Ulaanbaatar would simply change its time zone from 8 to 9 hours ahead of UTC on a designated date and time. If my guess is correct, it might be better for Mongolia to change its clocks in spring and not in autumn, as moving clocks forward in autumn works against the normal pattern of sunsets coming earlier in autumn. Also, it would make sense to review "Costs and benefits of time shifts", which summarizes scientific reviews of whether and when to change time zones. Please see: https://data.iana.org/time-zones/tz-link.html#costs Finally, I echo Nick's request in <https://mm.icann.org/pipermail/tz/2023-September/033044.html> for any information your government has about past time changes and boundaries between time zones in Mongolia, so we can correct any mistakes in TZDB concerning your country. Thank you.