Microsoft Windows Daylight Saving Time and Time Zone update now available (December 2009)
The most recent cumulative update to daylight saving time (DST) and world time zones (TZ) is now available for supported versions of the Windows Operating System via Microsoft Download Center and Windows Update.
Microsoft product teams follow a semi-annual DST and TZ update schedule, which follows the Windows regular schedule for publishing newly legislated DST rules and time zone updates. These annual Windows "Cumulative Daylight Saving Time and Time Zone Updates" are released in December for each calendar year; a semi-annual update will be released in August, as needed. Microsoft products that are affected may also schedule updates to accommodate some of these changes.
For more information about this cumulative DST and TZ update, visit the following Microsoft Web site: http://support.microsoft.com/kb/976098