Upcoming Windows DST Updates for Mexico, Mongolia and Iran

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Microsoft is preparing an update to address recent time zone data changes in Mongolia, and correct inaccurate time zone data for Mexico and Iran. Details are as below:

1. Mongolia

Mongolia will observe DST starting this year. Its DST period runs from the last Saturday in March at 2:00 AM, to the last Saturday in September at 00:00.

2. Mexico

A new time zone “Eastern Standard Time (Mexico)” was added in KB3039024 observing DST from the first Sunday of April till the last Sunday of October. However, according to the latest announcement from Mexico government, this time zone doesn't observe DST, thus the above DST rules are being removed in this update. 

3. Iran

Iran follows the Persian calendar and this update will correct Windows' "Iran Standard Time" DST data from year 2015 to 2024. 

This update will supersede KB3039024, and Microsoft is planning to release it to Hotfix server next week.