Problem:

Solution:

The behavior described herein applies to Groupcal 3.10 and newer.

There are 3 different approaches used to present all-day events; one when using Outlook client with Exchange Server, one when using Outlook Web Access with Exchange Server and one when using iCal—and they vary slightly, especially when the event is originated in one time zone and viewed in another time zone.

When using Groupcal, all-day events are presented in a way that's consistent with iCal but still retains accurate Exchange Server information.

An all-day event will be shown in iCal on the date the event starts. For example, an all-day event that was created in Outlook and starts on January 1 (regardless of the time zone in which it was created) will be an all-day event shown on January 1 in iCal (regardless of the iCal system's time zone).

An all-day event will remain in the time zone in which it was defined (i.e., when sync'd) only as long as neither the start date/time nor the end date/time is changed in iCal.

When the start and/or end times on an all-day event are changed in iCal, the event will be changed into the iCal system's local time zone and will be from midnight to midnight. This new/local iCal-set time will be used when next syncing to Exchange¹. Moving an all-day event in iCal (i.e., dragging it to a different location) immediately has the same effect (i.e., the start and end times are changed).

An all-day event created/modified in iCal will be sync'd into Exchange using the time zone the iCal system is in and will become a 24-hour event from midnight to midnight on the day in the iCal system's time zone. So if the Exchange client (Outlook or Oulook Web Access) is in a different time zone than the iCal system, you will see the times shifted accordingly.

Note that, although it's been time-shifted, it is still an all-day event ... it's just that Exchange only shows events as all day if they start and end at midnight in the viewer's timezone. In Exchange, all-day events are always (and must be) 24-hour events that start and end at midnight. Effectively, the iCal-modified all-day event becomes an all-day event in the local timezone of the iCal system and will be shown as an all-day event by an Exchange client only if that client is in the same timezone as the iCal system.

¹An all-day event created in iCal will use the iCal system's time zone that's set when the first sync operation, which includes that all-day event, is performed.