If you delete an entire calendar from your account, you can restore the calendar to your "Calendars" application. Each time that you delete your calendar, either part of it or the entire calendar, a copy of your deleted calendar or the deleted section will be automatically saved in the "Files" application of your account. It's from this backup file that you can restore your calendar to your account.
First, you'll need to go to the "Files" application and find the deleted calendar file that you want to restore. Follow the steps in the image below:
Once you have found the folder set in your account that has the "Calendar Saved Data" folder (generally this is the first folder set that was created in your account) you'll need to select the backup file that you want to restore. Follow the steps in the image below:
After you've downloaded the file, you'll need to go back to the calendar of your choice that you want to import this file into, or you will need to create a new calendar to import this file into. Follow the steps below for importing your calendar file:
This will open up the “Calendar Import” screen. Click the “Choose File” button to search and select the downloaded calendar file from your computer. Then, simply click the “Import Calendar” button.