Microsoft Knowledge Base Article 928388 contains the following INTRODUCTION:
Starting in the spring of 2007, daylight saving time (DST) start and end dates for the United States will transition to comply with the Energy Policy Act of 2005. DST dates in the United States 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).
The update that this article describes changes the time zone data to account for the United States DST change. This time zone update will also include changes for other related DST changes, time zone behavior, and settings. Some of these changes will occur in 2007, and some have occurred since these versions of Windows were originally released. The update that this article describes also includes some changes that have previously been released as individual hotfixes. An example of this is the Sri Lanka change in time zone offset. This update will also include some changes that have been individually documented in Microsoft Knowledge Base articles.
These updated time zone definitions will also be included with Windows Vista.
For more information about Windows Vista, visit the following Microsoft Web site: