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This article describes an update that makes time zone and daylight saving time (DST) changes in Windows for Brazil, Morocco, and São Tomé and Príncipe. Before you install this update, see the Prerequisites section.

This update applies to the following operating systems:

  • Windows Server 2012 R2

  • Windows 8.1

  • Windows RT 8.1

  • Windows Server 2012

  • Windows Embedded 8

  • Windows Server 2008 R2 Service Pack 1 (SP1)

  • Windows 7 SP1

  • Windows Server 2008 Service Pack 2 (SP2)

  • Windows XP Embedded

Note To get the update for Windows 10 and Windows Server 2016, install the latest cumulative updates that are listed in the Windows 10 and Windows Server 2016 update history Knowledge Base article.

Changes by location


Starting this year, Brazil begins its DST observance on the first Sunday in November instead of the third Sunday in October. Clocks in Brazil will move forward one hour on November 4, 2018 at 00:00 hours.

Time zone key name

Old DST start date

New DST start date

E. South America Standard Time

Central Brazilian Standard Time

Sunday, October 21

Sunday, November 4


As usual, Morocco is suspending its daylight saving time (DST) period for the observation of the Muslim month of Ramadan from 03:00 on Sunday, May 13, 2018, to 02:00 on Sunday, June 17, 2018, in the Gregorian calendar.

During this period, clocks are turned back to Standard Time to shorten the evenings, making it easier for Muslims to observe the Ramadan fast during daylight hours.

A Windows update will be made available in April for Windows XP Embedded, Windows Server 2008 SP2, Windows 7 SP1, Windows Server 2008 R2 SP1, and Windows Server 2012. No Windows updates are required for Windows 8.1 and later versions because those systems make the adjustments automatically.

Time zone key name

Display name

DST ends

DST resumes

Morocco Standard Time

(UTC+00:00) Casablanca

May 13, 2018 at 03:00

June 17. 2018 at 02:00

São Tomé and Príncipe

São Tomé and Príncipe moved from UTC+00:00 to UTC+01:00 on January 1, 2018 at 01:00 hours. A new time zone, "(UTC+01:00) Sao Tome," is being introduced for this region.

Time zone key name

New time zone display name

Sao Tome Standard Time

(UTC+01:00) Sao Tome

Update information

The update that is described in this article makes changes in the time zone and DST settings for Brazil, Morocco, and São Tomé and Príncipe.

For more information about how DST changes may affect other Microsoft products, go to the following Microsoft website:

General information about DST

For more information about how to configure DST settings in Windows, see the following article in the Microsoft Knowledge Base:

914387 How to configure daylight saving time for Microsoft Windows operating systems

Note When you apply this update, you may receive a message that resembles the following: 

Update cannot be installed as a newer or same time zone update has already been installed on the system.

This message indicates that either you have already applied the correct update or Windows Updates or Microsoft Update has automatically installed this update. No additional action is required to update the Windows operating system.


Learn about the terminology that Microsoft uses to describe software updates.

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