Daylight saving time changes for Mexico, Mongolia, and Iran in Windows

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials

This article describes a hotfix that updates daylight saving time (DST) settings for Mexico, Mongolia, and Iran. This update supersedes KB 3039024. Before you install this hotfix, check the Prerequisites section in this article.



A new time zone, “Eastern Standard Time (Mexico),” was added in KB 3039024. It was originally set to observe DST from the first Sunday of April through the last Sunday of October. However, according to the latest announcement from the Mexican government, this time zone does not observe DST. Therefore, the previous DST rules for this time zone are removed in this update.


Mongolia will observe DST starting this year. DST for Mongolia starts on the last Saturday of March at 02:00 and ends on the last Saturday of September at 00:00. The following DST rules will be observed.

Time zone key nameDisplay nameDST startDST end
Mongolia Standard Time (UTC+8:00) UlaanbaatarLast Saturday of March at 02:00:00.000Last Saturday of September at 00:00:00.000


Iran follows the Persian calendar. This update corrects the DST data for "Iran Standard Time" in Windows for the years 2015 through 2024.

Hotfix information

This hotfix applies to the following operating systems:
  • Windows Server 2012 R2
  • Windows 8.1
  • Windows RT 8.1
  • Windows Server 2012
  • Windows 8
  • Windows RT
  • Windows Server 2008 R2 Service Pack 1 (SP1)
  • Windows 7 SP1
  • Windows Server 2008 Service Pack 2 (SP2)
  • Windows Vista SP2
  • Windows Server 2003 SP2
  • Windows XP Embedded

How to obtain this hotfix

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must have the following update rollup or service pack installed for the indicated systems. There are no prerequisites to apply the hotfix to systems that are not listed here.
Windows 8.1 or Windows Server 2012 R2
Windows 7 or Windows Server 2008 R2
Windows Server 2003

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix replaces hotfix 3039024.


See the terminology that Microsoft uses to describe software updates.