Calendar is missing from watch

• Make sure on your iPhone the builtin Calendar app is not deleted

Restore a built-in app that you deleted

1. On your iOS or iPadOS device, go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap  to restore the app.
4. Wait for the app to restore, then open it from your Home screen.

If you have an Apple Watch, restoring an app to your iPhone also restores that app to your Apple Watch.

Adjust calendar settings

To change the kind of calendar notifications you receive and choose specific calendars to appear on Apple Watch, follow these steps:

1. Open the Apple Watch app on your iPhone.
2. Tap My Watch, then tap Calendar.
3. Tap Custom under Notifications or Calendars.

Do you have the Apple Calendar app on your iPhone?

If you have somehow deleted it, you can

Restore a built-in app that you deleted

1. On your iOS or iPadOS device, go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap  to restore the app.
4. Wait for the app to restore, then open it from your Home screen.

If you have an Apple Watch, restoring an app to your iPhone also restores that app to your Apple Watch.

Your Watch Calendar will be restored when you restore the Calendar back onto your iPhone.

Calendar support is part of watchOS. Check in the Watch app on the iPhone that you have setup everything for the Calendar.

If you go to the Watch app on the iPhone, if you go to Calendar, what do you see? Do you have the calendar setup on your iPhone?

What ckuan said. Calendar has to be missing from your phone.

You're welcome, enjoy.

You're welcome. Glad you were able to get it sorted out and working. Enjoy your devices.