My calendar is gone

More suggestions for the calendar issue ....

You can also try refreshing the calendar and see if the events reappear. Tap the Calendars button in the upper left corner of the app and them tap the circular arrow icon to refresh the calendar. You want to make sure that you have selected the correct calendar as well, if you have multiple calendars.

Try tapping in and out of different views on the calendar. Go from day view to month view, etc. Sometimes just playing around in the different views may bring the events back.

You can try closing the calendar app and reboot the iPad and see if the events come back.

Tap the home button once. Then tap the home button twice and the recents tray will appear at the bottom of the screen. Tap and hold down on any app icon until it begins to wiggle. Tap the minus ➖ sign in the upper left corner of the app that you want to close. Tap the home button twice.

Reboot the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider if it appears on the screen - let go of the buttons. Let the iPad start up.

If you backup with iCloud or iTunes on a regular basis - and I mean regularly - you might be able to recover the events by restoring from the backup. When you restore from a backup, you restore everything that is stored in the backup to the iPad. All of your app data and settings, notes, calendar entries, photos in the camera roll, etc. so when you restore from a backup, you "turn back the clock" on the iPad to the way that it was when you last backed up.