Before you run the Exchange Calendar Update tool, refer to Microsoft Knowledge Base article 941018, "How to address daylight saving time by using the Exchange Calendar Update Tool," for complete information about potential effects on your IT environment and user base.

After you install the DST updates for Microsoft Windows, all old appointments that occur during the DST change periods will be incorrectly displayed as occurring one hour later. This is true for both recurring and single-instance appointments. These appointments must be updated so that they will be displayed correctly in Outlook, in Outlook Web Access, and in CDO-based applications. Outlook provides a tool that is named the Time Zone Data Update Tool for Microsoft Office Outlook . This tool enables users to update their own calendars.

The Exchange Calendar Update Tool ("the Exchange tool") helps you avoid the challenges difficulties that are faced by administrators in deploying the Outlook tool widely to all users and to make sure that each user runs the Outlook tool correctly.