Yes. The Week view shows your week as a grid, with a row for each project, category and task and a column for each day. You can fill in the whole week at once, or enter time each day in Day view, whichever suits you.
Open Timesheets from the left menu and click Week at the top right. Time you've already logged that week is shown, along with your pinned rows.
Click Add Row. Choose the Project and Category, and a Task if you want one. Tick Pin this row to keep the row in later weeks too. Click Add.

Type the hours for each day. Use any time format, such as 1:30 or 1.5.
Click Save.

To start from last week's rows and hours, copy the previous week.
Add notes
When you click a day's cell and type its hours, a Notes box for that day opens below the grid. Type the note and click Save.

A small triangle in a cell's corner shows that it has a note. If a cell holds more than one entry, each one gets its own box.
Why a week won't save
A project's Timesheet Rules can ask for more than hours. Whoever manages the project sets them in Project Settings.
- Required task: with Require Tasks be selected on Timesheets on, you must choose a task when you add the row.
- Required notes: with Require Notes be entered on Timesheets on, new hours need a note in the Notes box.
- Completed tasks: with Don't allow tracking time on Completed tasks on, hours on a completed task are refused.
- 24 hours: one cell can't hold more than 24 hours.
- Locked time: approved time is read-only when your account locks approved timesheets. You also can't save hours before your account's lock date, unless you're an Administrator. See locking timesheets.
A cell with more than one entry for the same project, category, task and status is read-only here. Change it in Day view.
Change or remove time
Change a cell's hours and click Save. To remove a day's time, clear the cell and click Save. The cross at the end of a row deletes its time for that whole week. Invoiced time, and time on a bill, can't be deleted.
Week view records hours only. To record start and end times, use Day view.
Submit the week
If a project needs approval, click Submit for Approval to send all the week's draft entries at once. Save first: the button is disabled while you have unsaved changes. After you submit, you can still add hours to other days and submit those too. Draft, submitted and approved time for the same project, category and task show on separate rows. See timesheet approvals.

Administrators, Finance Managers and Portfolio Managers can fill in a week for someone else: choose the person at the top of the page. See editing another person's timesheet. To print or send a week, use the Timesheet Week View report.