Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
Have you checked the deleted items folder?
if all you did was delete the calendar entries and you did go to the deleted items folder and delete them from there too.
Then your en tries are still in the deleted items folder and you can recover / restore them back to your calendar.
Let me know if you get stuck or run into any issues, and I will assist you further as needed. And if this works for you please remember to click and submit a 5 star rating to show I was able to help you.
Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.