In August of 2005 the United States Congress passed the Energy Policy Act, which changes the dates of both the start and end of daylight saving time (DST). When this law goes into effect in 2007, DST will start three weeks earlier (2:00 A.M. on the second Sunday in March) and will end one week later (2:00 A.M. on the first Sunday in November) than what had traditionally occurred.

While the change in daylight saving time applies to U.S. and Canada, the change may impact customers based outside North America. Companies or organizations with operations, customers or vendors based in North America may be affected. In addition customers who interact or integrate with systems that are based in North America or rely on date/time calculations may be impacted.

Please note that Mexico will not be following the new DST 2007 rules with the U.S. and Canada. Accordingly such systems configured to use U.S. time zones (for example, Pacific Time) will need to change their system configurations to use the new Mexico time zones.

The change in DST will have an impact on many automated and technology reliant products. Individual consumers, small to medium size businesses, and large enterprises may be impacted by the new change in time. Computer-system related impacts include, for example:

In many cases, making the necessary changes to accommodate the new DST legislation will be a relatively minor task. Users may need to manually adjust the time on their devices when the change occurs.

In other cases, more substantial efforts may be required. In some cases, systems and applications may need to be updated directly, while in others, the application may simply inherit or "read" the date and time information from the underlying system that it resides on so the changes need only be made to that underlying system. Given the broad range of technology in use today—and the integration of systems between customers, vendors, and partners—business and IT managers should determine what actions should be taken to mitigate the impact of DST 2007 on their organizations.

Microsoft is committed to working with customers to make this transition as seamless as possible for customers affected by these new time changes. We are further committed to working with others in the industry to address the broader challenges presented by this U.S. statute.

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Microsoft products affected by 2007 DST changes

Several Microsoft products are affected by DST. Updates to these products are being developed and tested. Some of them are currently available, with the remainder scheduled to be released from December 2006 through early March 2007.

Depending on the particular product or scenario, these updates will be released through Microsoft Customer Support Services (CSS), Hotfixes incorporated in Knowledge Base articles, Windows Update, Microsoft Update, Windows Server Update Services (WSUS), and the Microsoft Download Center.

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What end users can do to ease the transition

All users of Microsoft products affected by the time change should give extra attention to appointments scheduled during the extended DST period (March 11, 2007 to April 1, 2007 and Oct 28, 2007 to November 4, 2007). Users should view any appointments that fall into these date ranges as suspect until they communicate with all meeting invitees to make sure that the item shows up correctly on everyone's calendar both internally and externally. To minimize confusion during the affected date ranges:

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Supporting the DST changes on Windows operating systems

Updated time zone definitions will ship with Windows Vista, however earlier versions of the operating system will need an update. For Windows XP Service Pack 2 (SP2), Windows Server 2003, and Windows Server 2003 Service Pack 1 (SP1), Microsoft will release a single global time zone update which will include changes for the United States DST change. This time zone update will also include changes for other related DST changes and time zone behavior and settings that will take place in 2007 or have taken place since these versions of Windows were originally released. It will include some changes that have previously been released as individual hotfixes (such as the Sri Lanka change in time zone offset) or have been individually documented in prior Knowledge Base articles.

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Preparing other Microsoft software products for the 2007 DST changes

For many of the Microsoft products affected by the 2007 daylight saving time change, the most recent versions will not require an update. However, earlier versions of these products will require an update, as shown below. Find more information on Microsoft Support Lifecycle.

Outlook

To display the correct time for meetings scheduled during the extended DST period, end users will need to have their operating systems patched such that it reflects the new time zone definitions.

Users will then either manually change the Calendar time zone (available from the 'Calendar Options…' dialog on Tools | Options) or respond to the automatic prompts to change their Calendar time zone that will occur 1 to 7 days after the DST rules are updated on the machine.

Without an update, the following will occur for Outlook calendar items that are active during the weeks of March 11, 2007 to April 1, 2007, and October 28, 2007 to November 4, 2007: Appointments and reminders will appear one hour earlier than they should. All-day events will shift and span two days because these events are associated with 24 specific hours rather than an individual date.

Microsoft has incorporated a new feature into Microsoft Office Outlook 2007 to help adjust calendar items affected by time zone changes.

For other releases of Outlook, Microsoft will release an Outlook Data Update Tool. This tool is scheduled for release in January and will be available in the Download Center.

Exchange Server

Microsoft calendar software such as Outlook depends on the operating system time zone information to display time information. However, Collaboration Data Objects (CDO)-based programs such as Outlook Web Access depend on separate internal time zone tables. This update modifies these internal time zone tables to match the changes in time zone settings. Without this update, calendar items in CDO-based programs will operate as if standard time is in effect during the extra weeks of daylight saving time.

For Exchange Server 2003 Service Pack 2 (SP2), Microsoft will release a global time zone update in January 2007 which will include changes for the components affected in Exchange Server. This time zone update will also include changes for other related DST changes and time zone behavior and settings that have taken place since Exchange Server 2003 was originally released. It will also include changes that have previously been released as individual hotfixes.

A test version of this update is now available to businesses that wish to test the impact of the upcoming time zone changes. A copy of the update can be downloaded from the Microsoft Download Center. For more information please refer to Knowledge Base article 926666. Please note that by the time that the final update is released to the public, Exchange Server 2003 SP1 will have passed the end of support date and will not receive the update. Find more information about support policy lifecycles.

If you are running Exchange 2000 or Exchange 5.5 and are under an Extended Hotfix Support Agreement or Custom Support Agreement, please contact your Technical Account Manager for more information.

Windows SharePoint Services

For Microsoft Windows SharePoint Services 2.0, Microsoft will release a single global time zone update which will include changes for the United States and Canada DST change. This update will be made available on January 9, 2007 via the Microsoft Download Center and released through Microsoft Update on January 23, 2007. To ensure your SharePoint timestamps and calendars are correct; apply the update between January 9, 2007 and March 10, 2007.

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Additional resources

Windows operating systems

Other Microsoft products