After switching over our email from self-hosting to GMail, my Sr. SysAdmin is looking for us to consolidate our company calendars into one singular Google Calendar.
With our current system, if a user marks a vacation day, only the Office Manager is able to go back and edit the entry after that date (to prevent people from giving themselves free vacation days).
As far as I can tell, with Google Calendar, if the calendar is shared company-wide, any user can create, edit, and/or delete an event. Is there a setting somewhere to restrict access to completed events?
No, there is not possible restrict permission to add/modify. Currently is possible to choose these permissions:
To protect your data when someone deletes an event, you can track changes with the Notifications: https://support.google.com/calendar/answer/37242?rd=1
This is a bad system because anyone can delete your events. There should be a way to share an event but only allow it to be deleted by the person who put the event in.