Has your colleague done or said anything to make you suspect he is being forced into working longer than he should? How well do you know him? There's a good chance that he is aware that he works many more hours than his peers, and probably wouldn't be surprised if someone asks about it.

@Kozaky No he didn't. I sometimes help him with work since I'm more experienced with some of our stuff, but other than that we don't talk about the work environment. I think he's aware that he works way more as the building is empty on Sundays and public holidays, I just want to be sure he doesn't feel that he has to.

Does said colleague have a regular working contract, is he "employed" or is he on some kind of freelancer/studying relationship?

@nvoigt I don't know exactly to be honest, but if it's some kind of a student's relationship, this would really open another view if he pursues his own goals. Good point!

How do you know that he works on public holidays? You seem to be there when he is.

@CaptainEmacs As I wrote, I live pretty close to the building and see our offices from outside.

Ok. Do you know that he actually works?

No, I see him but don't check what's on his screen.

You mention that you work in a research institute. What you describe is pretty normal in academia: I and all of my peers very often worked long hours and weekends on our research. Are you sure this is so unusual where you are? I have never worked at a research institute where people didn't often come in on the weekend. What is your field? Is it experimental? Running experiments often requires working odd hours.

How long has this guy from China been working in Germany? You think nobody in HR or recruiting or his manager ever bothered to tell him about working hours expectations? And you think he isn't smart enough to have looked around and seen that nobody else is working when he is working? And you think it's your role to straighten him out?

@JoeStrazzere A few months. Yes, I think probably nobody brought this up. I think he knows he's the only one (especially as the office is empty in some days), but probably thinks he's expected to anyways for whatever reason. No I don't think it's my role, that's why I'm asking.

@terdon In our department, I know it is unusual (as I wrote, sometimes is "normal" but not every weekend plus the whole easter "vacation"). We are more or less a data science department in a large governmental somewhat biological facility.

So you're saying there's an employee, X, who is highly incompetent. If it's your company, just fire X. If it's not your company, and they don't fire X, perhaps you should question whether it is the sort of place you want to work.

The idea that X "doesn't realize" he should not stay more than 35, 40 hours at the office, is not very sensible.

@Fattie how did you get to that conclusion? Nowhere in the question it says that X is incompetent. Also, I think dismissing the possibility that he doesn't realize it, is not very sensible either.

@Cyonis - I see what you mean: I just take it as a given that anyone who "works" (shows up at the office) more than about 40, 45 hours is totally incompetent.

@Fattie On what grounds did you base such opinion to take it as a given?

Is there any chance he doesn't have a place elsewhere to live?