In order to control timesheet periods, did you know there is a feature to control which weeks are available for time entries and override on a per-user basis?
The internal switch in OpenAir called Enable timesheet open/closed periods, if enabled, makes the Timesheet open periods available as a company setting. This is available via Administration > Application Settings > Timesheets Settings > Other Settings.
The Timesheet open periods allows the admin to indicate which timesheet periods are available and open for end users to log time to.
Example: If the timesheet duration is set to Weekly, enter the Open Periods as follows:
Note: Do not enter or include spaces before and after the hyphen on the date ranges as they are not accepted by the system.
The admin will then remove the periods from the list so that users are no longer able to log time against them. They should then be able to see the open periods on their timesheets and only be able to log time to these open periods.