There are daylight time changes coming in mid March and unless you update your system, your computer time will be wrong and once you do, appointments falling in the affected periods will be off an hour (Mar 11 - Apr 1 and the first week of Nov).

Windows update will install a patch that reflects the new daylight times, but only on Windows XP and 2003 systems. Users of older OS's will need to make the changes themselves. (Vista has the changes included.) If you use Outlook 2007, it should offer to fix your appointment times on the next restart after the time zone update is installed. If you use an older version of Outlook there is a tool you can download to fix your appointments. (These tools are also good for changing appointments if you move to a new time zone.)

The time zone update tool is found in Outlook 2007's Tools, Options, Calendar options dialog or can be downloaded from Microsoft.

More info and links to the Outlook update tool (works with v. 2000 to 2007) and the Exchange Server Time Zone Update Tool are at http://www.slipstick.com/emo/2007/up070104.htm#tz

DST Wizard to help guide you to the changes you need to make:
http://www.microsoft.com/windows/timezone/dst2007.mspx

Time Zone updates:
US and Canada: http://support.microsoft.com/kb/928388/
Western Australia: http://support.microsoft.com/kb/929120/

More time zone information: http://www.microsoft.com/windows/timezone.mspx