Daybook
Plan the day. Sign it off in ninety seconds. That is the timesheet.
Planning lives in one tool and tracking lives in another, so the same information gets entered twice and the second entry quietly stops happening. Daybook keeps a single record that carries both the plan and the actual. The timesheet becomes a by-product of having planned, and the variance between intent and reality falls out for free.
The part that earns its keep
There is no live timer to keep up with. A running clock only tells the truth if you remember to switch it every time reality changes, and one missed switch bills two hours to the wrong task while looking authoritative.