Issues can be edited right in the Calendar: trimed or extended, drag and dropped to other dates. All calendar changes affect issues' start and end dates.
If you are using Date picker field type (as in example) issues are placed for whole day and the finish date is set 00:00 or 12:00 AM of next day.
Edit issues is available to the users accordingly user's permissions.
Remove from calendar clears start and end dates fields.The user performing this must have permission to edit issues in project permission scheme.
Remove from JIRA removes issue completely. The user performing this must have permission to remove issues in project permission scheme.