Hi @Tiffany Wood ,
Do you mean that when you delete an unwanted calendar, you delete the calendar you need as well? What is the relationship between these calendars? You could recover your calendar by following the steps below:
1.Go to Folders view
2.In the deleted items folder, right-click the calendar you want to recover and click Move Calendar
3.Click Caldendar and Click OK
4.The calendar will be recovered
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