You can track the time you've spent working on tasks, projects, and non-project activities by using timesheets in Project Web App.
Note: Before you can create a timesheet, the site administrator needs to set up time reporting periods for your organization. If you follow the steps in this article and don't see any links to create a new timesheet, it's possible that your site administrator hasn't set up reporting periods yet.
To create a new timesheet:
On the Quick Launch, under My Work, click Timesheet.
To create a timesheet for a reporting period other than the current one, on the Timesheet tab of the Ribbon, click Select Period.
Choose a date within the reporting period for that timesheet, and then click OK.
The timesheet will automatically contain all of your project tasks, with work planned for the period, as well as any standard non-project activities.
For more control over what data is pre-populated in a new timesheet:
On the Quick Launch, under Settings, click Manage Timesheets.
Place the mouse cursor over the Click to Create link in the Timesheet Name column for the timesheet in the period you want to create, and then click the arrow that appears.
Choose a method for pre-populating your timesheet: Create with Default Setting, Create with Tasks, Create with Projects, or Do not Autopopulate.
From here, you can choose to add lines to your timesheet, enter actual work, or, if you've completed your timesheet, save it or submit it for approval.
Note: If your organization uses single entry mode to capture timesheet data and task status information using a single view, your timesheet will also show overdue tasks.