Rewind back to 1999... As the year progressed, did you stock up on food, water and other "provisions"? 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.
Why didn't we just abolish the darn thing?
Anyway, if you are concerned about the impact of the time change on your software and computer systems, see http://support.microsoft.com/gp/dst_overview for a consolidated view of the changes in Microsoft software.
[UPDATE] See http://office.microsoft.com/en-us/outlook/HA102086071033.aspx for information on Office.