When hovering over task bar, you see start and end dates, e.g. “Tue, 4/1/25 to Fri 4/25/25”.

Add duration to it, e.g. “Tue, 4/1/25 to Fri 4/25/25 (19 days)”.

Sometimes we are quoted efforts from 3rd parties, in “number of work days it will take” and we manage them with this metric later on.

Hovering would be easier, than having to start to drag the task edge (without accidentally changing a start or end date), to reveal the # working days. Hovering is also easier than having to count them by opening the task info dialog and looking at the pop-up calendar used in date selection.