Ask HN: How do you maintain timesheets?

This applies to both freelancers and employees.

As a freelancer I was using multiple spreadsheets or some combination thereof to maintain the billable hours.

As an employee, although we have an application to maintain times spent against bug / tasks etc, I feel a lot of times this gets fudged because the goal becomes to total 8 hours instead of logging the actual times. (Goodhart's law)

Additionally, it's not that all the 8 hours (usually more!) gets spent on work. There's a couple of breaks we take besides spending some time on ourselves (maybe browsing HN)

If maintaining a spreadsheet is a solution, then can someone suggest a format which can then be analyzed programmatically later?

If an desktop / mobile application helps I would like to know about those too.