You can modify both the author date and the commit date on a commit if you need to. Git log is not trustworthy spying tool.
If you are at the point where you need to modify commit timestamps to satisfy some micromanager, it's highly likely that there are other things wrong with them that will lead to you searching for a new job fairly soon.
* you otherwise liked the job
All I was saying is that these two are very likely mutually exclusive.
Sure, it's hypothetically possible that I have a micromanage-y boss who only tracks my commit times and nothing else. But really? That's the same boss who's going to mentally think you're "not a team player" because you left an hour early for your son's birthday party. That's the same boss who's going to obsessively tracks how many vacation days you "accrued" and insist on you coming in when you're sick if you don't have any left. Let's not kid ourselves.
Not really sure what the benefit in cheating your boss would be though? You still had to do the work at some time. Maybe you work extra hard one day but push only the first half of your commits, then give yourself a day off where all you do is check in at the end to push the fake-timed other half of them?
It'd probably be easier to find an 'unlimited holiday' job that pays you for output rather than keeping your seat warm.