Project Server FAQs -> PWA FAQ 1

Can I updated my timesheet on a weekly basis if the default setting is day by day? MS Project Server 2003: Yes, you can go into View Options when you are in your timesheet view and set units from days to weeks. This will not always allow you to update tasks and you will receive an error message when trying to update tasks that do not have any scheduled work. Please read for more details: View Options (Tasks with Date Range)