A special note to users of Microsoft Outlook on a Windows Mobile-based device: an update for Windows Mobile will be available on the Web by February 12, 2007. To download this update, visit the following Microsoft Web site on or after February 12, 2007: http://www.microsoft.com/windowsmobile/daylightsaving [link updated]
"If you do not update your Windows Mobile-based device, the clock on the device will be incorrect by one hour when daylight saving time (DST) changes occur. Specifically, calendar items will incorrect by one hour during the extended DST period. This period lasts for three weeks in March and for one week in November."
And see http://support.microsoft.com/default.aspx/kb/923953 for more details.