Agreed. When I was younger, for multiple reasons but mostly stupidity, I was 30m to 1h30 late at work every. single. day. And the official work day started at 9:30am, so it wasn't that bad to begin with. In my defence I must add that I never left before my full 8 hours were over.

I was in good terms with everybody, managers as well, and I think in that stupid age I did some brilliant work I'm still very proud of. After a couple of years, when all the rumors about me being hired fulltime were materialising (I was working for them through an agency), they just decided to let me go.

It hurt at the time, but it was a good decision that served me as a lesson[1].

Employers, unless you're a bank with set opening times, don't fret over 10 or 20 minutes. Programmers are productive only in a stress-free environment. Obsessing over 10 minutes is the total opposite of that. But please fire engineers like me, you'll do them a favour.

1: I stopped being so late in future jobs, but I also discovered I have some kind of DSPS. It's still bad, but I'm now a freelance (in Europe) working for US companies, my clients are having their coffee when it's 3pm here.