Outlook Calendar displays working hours as grey
In the Calendar module of Microsoft Outlook and when you use the Scheduling Assistant, some calendars of shared mailboxes or rooms display working hours as having a grey background while other calendars display working hours as having a white background. This issue occurs while Outlook is connected to Microsoft Exchange Server. In other clients, such as Outlook Web App (OWA), the working hours of all calendars are displayed as white.
Original KB number: 4488050
This behavior is expected if the following conditions are true:
- Outlook is connected to a newer version of Microsoft Exchange Server that hosts mailboxes and calendars.
- The working hours of the client and the mailbox are in the same time zone. Outlook cannot yet handle all the new elements that are used by newer versions of Exchange Server. These elements include WeekDays, WeekendDays, and AllDays. For more information about the new elements in Exchange Server, see [DaysOfWeek Enumeration](/previous-versions/office/developer/exchange-server-2010/ff343675(v=exchg.140).
Microsoft is aware of this issue and will update this article when a fix becomes available.