Help

How do I back up?

Please use the backup function of your calendar.

iCloud Calendars

Open "Setting" app on your iPhone
Show iCloud Settings
Tap "iCloud"
Turn on "Calendar"

Check the above settings and back up on iCloud.

References

Apple Support: About backups for iOS devices
Apple Support: How to back up your iPhone, iPad, and iPod touch
Apple Support: If iCloud Backup couldn’t be completed or you can’t restore
Apple Support: How to back up iCal calendar data
Google Help: Export your Google calendar