We recently had a server failure that resulted in having to rebuild the server services. Ended up going from mySQL 5.1 to 5.6.23. Since that issue occurred, one of our clients is reporting that Calendar gives him this error when trying to create new events:
A Database Error Occurred Error Number: 1364
Field 'last_date' doesn't have a default value
Client reports that entry gets made, just doesn't have an date info in the Calendar field.
It's EE 2.8.1 and Calendar 1.8.9.