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Microsoft Graph only shows 10 calendars

Microsoft Graph returns a maximum of 10 calendars per account. If your mailbox contains more than 10 calendars, any calendars beyond the first 10 will simply not appear in BusyCal — or any other app that syncs through Microsoft Graph.

This is a server-side limit imposed by Microsoft, not by BusyCal. The 10-calendar count includes Outlook's built-in calendars such as Calendar and Birthdays, which cannot be removed — so in practice you can have up to 8 user-created calendars.

Symptoms​

  • Some calendars are missing after adding an Office 365 (Microsoft Graph) account to BusyCal.
  • The same calendars appear normally in Outlook, Apple Calendar, or BusyCal via EWS, but not via Microsoft Graph.
  • Removing a calendar from the account causes a previously missing calendar to reappear (they come back in the order they were originally added).

How to fix it​

  1. Count how many calendars exist on the account in Outlook (including Calendar and Birthdays).
  2. If there are more than 10, delete or archive the lesser-used calendars until the total is 10 or fewer.
  3. In BusyCal, choose View > Refresh to re-sync the account.

The previously missing calendars should now appear.

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