ErrorCalendarInvalidTimeZone: Calendar items cannot be processed because your client access Exchange server is missing a definition for the reference UTC / GMT time zone.
To verify if the UTC / GMT time zone is missing using OWA:
- Open OWA (Outlook Web Access) for any mailbox
- Go to Options (right hand corner)
- Select Regional Settings
- Expand the Current Time Zone combobox
- Check if (GMT) Coordinated Universal Time is present (see attachment)
- Cancel changes (only check if the time zone is defined - do not change it)
To verify if the UTC/ GMT time zone is missing using the Windows registry:
- Login to the Exchange Server(s) providing client access
- Start regedit
- Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones
- Check if a UTC registry sub-key is present (see attachment)
Once you have verified the problem, ensure the reference UTC/GMT timezone is defined on your Exchange server.