Perspective from the management side at a consulting place: We don't want or need you to log your time to the minute. It's counter-productive and a waste of time. It needs to just be representative and not dishonest (please read that sentence twice).
An hour long meeting booked, that ended up taking 45mins? It's an hour. It's the same reason we don't expect you to stop recording time when you to down the hall to make a coffee or take a bathroom break. The numbers only really makes sense at the aggregate level, and going to a higher level of detail is not reliable because of all the noise and different ways people measure their time.
My experience with timesheets is that they must add up to the hours you're paid for (full-time salaried work, not hourly consulting). That more-or-less guarantees that timesheets are made-up.
My first salaried job was as a salesman; we incurred expenses, which we could claim back. It was explained to us that the system was there to ensure that we weren't out-of-pocket; claims didn't have to actually be true, but you did have to have incurred the expense.
I fairly soon realised that this was a lie; the expenses system was really a salary-augmentation scheme, and you were expected to inflate your claims. Everyone was at it.
8 hours of sleep can undo less than 4 hours of problem-solving activity. Our large brains are already consuming too much body resources.
I have CO2 monitor, which I use to estimate is my brain working or not: when I'm working, CO2 level raises quickly above 1000ppm, so I need to ventilate my room often; when I'm idling, e.g. by playing a simple game, CO2 level is at about 740-790ppm without ventilation for whole day.
When I'm returning from work, I see at CO2 monitor that my head is still working. Yes, I'm able to «work» sustainable 4h per day only, but «work related activity» consumes my brain for whole day.
An hour long meeting booked, that ended up taking 45mins? It's an hour. It's the same reason we don't expect you to stop recording time when you to down the hall to make a coffee or take a bathroom break. The numbers only really makes sense at the aggregate level, and going to a higher level of detail is not reliable because of all the noise and different ways people measure their time.