An expired or otherwise invalid Calendar API sync token can produce HTTP 410 during incremental synchronization. Google’s guidance requires a new full synchronization in that case. Distinguish the application’s replaceable local mirror from the user’s actual calendar data before implementing recovery.
Identify the failed synchronization
Record the affected calendar collection and query configuration without logging sensitive token values or event contents unnecessarily. Google’s guide says token invalidation can result from expiration or related ACL changes. A 410 is not simply another transient request to repeat indefinitely.
Rebuild the appropriate local mirror
Discard the invalid sync state and rebuild the relevant cached collection through a new full list operation, processing all pages. Google’s wording about wiping the client store concerns the local synchronized state. It is not an instruction to delete events from Google Calendar or remove unrelated application records.
Preserve independent unsynchronized user work through an appropriate conflict or recovery design. A cache reset should not silently erase data that exists only locally and has not been confirmed in the remote calendar.
Verify the new baseline
Obtain the replacement nextSyncToken from the final full-sync page and store it with the rebuilt collection. Confirm expected records and then test a subsequent incremental change in a controlled environment. Recheck permissions when ACL changes may explain the invalidation. Keep a partial rebuild visibly incomplete until its final page and token are committed. The completed recovery should establish a new verified local baseline without changing the remote calendar merely to repair a synchronization cursor, and without claiming that an empty intermediate cache proves the user’s events were deleted.
References
Reviewed against the linked official product guidance on November 4, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.