This is a known issue which has an improvement request here. If this is an important feature for you, I encourage you to vote, comment, and watch this issue. That way you'll improve it's visiblity to developers, and get updates if they decide to implement this.
Right now the only way you would be able to prevent a user from permanently deleting a calendar would be to restrict their editing permission completely.
But I do have good news! :) Whenever someone deletes a calendar entirely, Confluence will e-mail a backup file of it to anyone who was subscribed. You can also use this backup to restore the calendar.
Badges are a great way to show off community activity, whether you’re a newbie or a Champion.Learn more
Any other country that celebrates Midsummer holiday (this friday 22 June)?
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG