Timesheet approval allows you to mark as read-only all time time entries from a specific date range. Further, it prevents users from adding new time entries to that same date range. You must be an admin to approve timesheets.

• Go to Time Tab and select the first view "Timesheet Approval"
• Select a pre-defined or custom date range
• Click "Approve" button
• Click "OK" in pop-up dialog to confirm
• Clicking previously approved timesheets displays all approved time entries in a new browser window (that you sort, filter or download)