In 2007 the USA and Canada will move the start of their Daylight Saving Time forward by three weeks (in the contiguous states, but not in Hawaii and a few other places) and extend its duration by four weeks. If you are in the US then most likely you already know about it. Microsoft just released an update for Windows to ensure that it will automatically set DST for US timezones on the correct dates:
http://www.microsoft.com/windows/timezone/dst2007.mspx
http://aa.usno.navy.mil/faq/docs/daylight_time.html
If you are outside the US do you need to take any action? Perhaps. Do you have any schedules that interact with a US timezone (such as time-sensitive data feeds, notifications or reports)? Do you make any time-based computations that are affected by timezone differences in international data? Do you have any SLAs that include time constraints for your US customers? If any of these apply to you then be aware of the change. Here in the UK for example it means that US DST starts 2 weeks before BST instead of the usual 1 week after.
Updates are promised for Outlook, Sharepoint and Exchange.