[Hafrust]

This is from Microsoft, hopefully it will help:

Installation tips

• Run the Outlook Time Zone Update Tool on your PC immediately after you apply the DST update
  After you apply the DST update to all of your PCs, run the Outlook Time Zone Update Tool on your PC immediately. If meetings between extended DST periods are scheduled after the DST files are installed but before the tool is run, meetings will erroneously be moved one hour earlier. To correct such calendar items, organizers should manually update such meetings to ensure they are scheduled accurately for themselves and all invitees. More information about Outlook Time Zone Update Tool is available at http://support.microsoft.com/kb/931667.
• All connected devices must be updated
  Even if you correctly update your PC with the DST update, when you view your calendar from a non-updated mobile device running Windows Mobile, your meetings during the extended DST period will be shifted by one hour. Meetings created on your non-updated device will need to be updated on your PC by running the Outlook Time Zone Update Tool again.
• If some users have not updated their Outlook, it will affect other users
  The Outlook Time Zone Update Tool only updates meetings for which the user is the organizer, and then automatically sends updates for those meetings to attendees. Meetings that you are invited to but did not organize will not be updated until the organizer updates the meeting and sends you an update. Once the update is accepted, it will display at the proper time. Additionally, meetings created by a delegate on your behalf from a non-updated PC will need to be updated on your PC by running the Outlook Time Zone Update Tool again.