How to Fix iPhone Calendar App Not Syncing

Calendar not syncing on iPhone is usually caused by the wrong sync settings, an account connection issue, disabled calendar visibility, or delayed iCloud or Exchange updates. A quick fix is to check internet access, confirm the correct calendar account is enabled, refresh Calendar sync, and verify that missing events are not hidden in an unchecked calendar list.

Steps

1. Open Settings > Calendar > Accounts and confirm the correct account is still signed in. Turn Calendars on for iCloud, Gmail, Outlook, or Exchange if the toggle is off.
2. Open the Calendar app, tap Calendars, and check whether the calendar with events missing is selected. Hidden calendars often look like a calendar sync problem.
3. For iCloud calendars, open Settings > [Apple ID] > iCloud and turn Calendars off, then on again. For Google or Outlook, remove and re-add the account from Settings > Calendar > Accounts.
4. Check Settings > Calendar > Sync and set a broader range such as All Events if older entries are missing. Limited sync ranges can make events appear deleted.
5. Restart iPhone and update iOS from Settings > General > Software Update. Temporary bugs and outdated system files can interrupt calendar not syncing issues.

Common Issues and Fixes

• Events missing after account change — The likely cause is a disabled account or expired sign-in. The fix is to re-enter account credentials and confirm the Calendars switch is enabled.
• Some calendars show, others do not — The likely cause is hidden calendar lists inside the Calendar app. The fix is to open Calendars and manually select every needed calendar.
• Old events are gone — The likely cause is a restricted sync window. The fix is to change Calendar > Sync to All Events.
• Work calendar does not update — The likely cause is a server delay or Exchange policy issue. The fix is to remove the work account, add it again, and confirm sync is allowed by the mail administrator.
• iCloud calendar updates on one device only — The likely cause is poor network access or iCloud sync interruption. The fix is to connect to stable Wi-Fi, confirm iCloud Calendars is on, and restart both devices.

Quick Tips

• Shared calendars may stop updating if sharing permissions were changed by the owner. Re-accepting the invite may be required.
• Time zone mismatches can make events look missing when they are only shifted to a different hour or day. Check Settings > Calendar > Time Zone Override.
• Imported subscription calendars do not always refresh instantly. Some subscribed calendars update only at scheduled intervals.
• Deleting an account from iPhone can temporarily remove local calendar data until the account syncs again.

Related Questions

Why are iPhone calendar events missing but not deleted?

Events missing are often hidden by calendar filters, limited sync range, or account sign-out. Checking visible calendars and account settings usually restores the entries.

Why is Calendar syncing with Gmail or Outlook so slowly?

Google and Outlook sync may be delayed by background refresh limits, weak internet, or account authentication errors. Re-adding the account often fixes the calendar sync problem.