You can track any changes made to your timesheet via running a "Timesheet Audit Trail Report".
To create this report please follow the steps below:
> Login to your instance. > Click on Reports Tab. > Click on New report, in the pop up choose "Timesheet" as category and Report type as "Timesheet Audit Trail Report", click on create. You can add columns of your choice in this report. > Use filters to select or deselect relevant options and run the report.