Time rollup is available for Business and higher accounts, regular, and admin users can enable and disable time rollup.
The Time spent attribute in projects allows you to see how much time was spent on the tasks it contains. You can rollup this number to automatically calculate the time spent on all the tasks in the project.
Time rollup can be enabled for single projects in their project info panel or for multiple projects in Table view.
From the project info panel:
Navigate to the relevant space.
Click a project to open its project info panel.
Hover over and click the icon to the right of Time spent 1 to enable or disable time rollup.
To disable rollup repeat Step 3 and click again to Disable Dates Rollup.
From Table view:
Navigate to the space, folder, or project that contains all projects that you want to rollup the time spent.
Switch to Table view.
Make sure that the Time spent column is added to the view. If not, click the gear icon 1 and check the box next to Time spent 2.
Right-click the Time spent column title (or click the caret icon) 3 and hover over Rollup 4 in the drop-down menu.
Select Enable/Disable for all projects 5.
Click Enable in the confirmation that appears.
You'll see the total number of hours spent on a project in the cell. To edit the values, switch to the Timelog view or open each task separately and edit the values from Task view.