1)If you are unable to change the backdated timesheet before the restricted date then follow the following step:
Goto --> Tcode CAC1 and change the lower limit to the required backdated weeks. This should work unless something is hard coded.
2)If still it is not working then GOTO -->Tcode SMOD --> CATS0003 --> Click on component --> chk the user exit --> check if time sheet data is hard coded to limit the number of days to 90 days backdated to save the time sheet data.
This would definelty help
