CalSync for Mac
Keep your work, university and personal calendars honest about when you are busy.
CalSync is a menu bar app that mirrors busy time between calendars in different organisations.
Connect a Microsoft 365 account, a Google Calendar or the calendars already on your Mac, and every
booked slot in one shows up as a "Busy" placeholder in the others. Titles, attendees and notes never
cross over. Everything runs on your Mac; there is no CalSync server.
How it works
- Add two or more accounts in Setup. Microsoft 365 uses a sign-in code in your browser;
Google opens its consent page; Apple calendars need Calendar permission once.
- Choose a direction per account: two-way, share only, or receive only.
- CalSync syncs on launch, on a schedule (15 minutes by default), after you edit a local
calendar, and when the Mac wakes.
- Placeholders are tagged so CalSync only ever deletes events it created itself. Removing an
account cleans up its placeholders first.
Support
Something not syncing? Open Setup and use Copy log, then email the
log to siim.vene@gmail.com. The log contains account
names and error messages, never event details.
Common questions:
- Microsoft asks for admin approval. Some organisations block third-party
apps; ask your IT department to approve CalSync, or use the personal account path.
- Nothing appears in a calendar. Check that the account is set to two-way or
receive only, and that at least one other account shares its busy time.
- Placeholders are still there after removing an account. Cleanup is
best-effort; delete any leftover "Busy" events by hand, they are ordinary events.
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