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December 2011 cumulative time zone update for Windows operating systems

Article ID: 2633952 - View products that this article applies to.

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SUMMARY

Important This update supersedes and replaces update 2570791

(http://support.microsoft.com/KB/2570791)

, which was released in August 2011. No additional time zone changes were released as hotfixes after update 2570791

(http://support.microsoft.com/KB/2570791)

was published.

If you have already deployed update 2570791

(http://support.microsoft.com/KB/2570791)

, read the descriptions of the specific time zone changes that are addressed in this article to determine whether you must deploy this update immediately. If systems are not directly affected, you can schedule deployment at the next available opportunity.

We recommend that you deploy the most current Windows cumulative time zone update to guarantee the consistency of the time zone database on all systems.

Important

Before you apply the update that is described in this article, be aware of potential issues that may affect Microsoft Outlook.

For more information about these issues, view the article in the Microsoft Knowledge Base:
931667
(http://support.microsoft.com/kb/931667)
How to address time zone changes by using the Time Zone Data Update Tool for Microsoft Office Outlook
If you are running Microsoft Exchange Server in an Information Technology (IT) environment, you must take additional measures to guarantee the correct operation of Exchange Server.

For more information about the Exchange daylight saving time (DST) update, view the article in the Microsoft Knowledge Base:
941018
(http://support.microsoft.com/kb/941018)
How to address daylight saving time by using the Exchange Calendar Update Tool
Cumulative time zone updates contain only data that has changed for a specific region or that was added to maintain parity with other operating system versions. Therefore, if a time zone key is deleted, some original values may not be restored after you apply the cumulative zone update.

We do not recommend that you delete any registry keys that are related to time zones. On a computer that has incomplete time zone keys, first restore the time zone keys from a known good backup. Then, apply the update.

MORE INFORMATION

The update that this article describes changes the time zone data to accommodate daylight saving time (DST) changes in several countries.

The update that this article describes is a cumulative update rollup that includes all previous windows time zone changes. For more information about how DST changes may affect other Microsoft products, visit the following Microsoft website:

http://support.microsoft.com/gp/cp_dst

(http://support.microsoft.com/gp/cp_dst)

For more information about how daylight saving time changes may affect other Microsoft products, view the following article in the Microsoft Knowledge Base:

914387

(http://support.microsoft.com/kb/914387)

How to configure daylight saving time for Microsoft Windows operating systems

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

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

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

The following files are available for download from the Microsoft Download Center: