I heard about the OS one, sounded super cool and also a lot of work from what I gathered. Heard about it too late and required a buddy. Oh well, can't have it all.
[1]: faculty of math and natural sciences
I can't remember exactly how many, but once you included lectures, scheduled labs and tutorials, was not that far from 9-5 (minus the standard university-wide Wednesday afternoon sport slot).
The friends would go quiet and say "oh, we have 12".
And that didn't even incude the "non-contact" hours in the labs grinding the coursework until security shooed us out late at night so they could lock the building. Good times (in retrospect, especially).
Plus in one term there was some miscommunication between the professors and they set us one experiment every week instead of every two weeks, I remember literally working like 12 hour days on the weekends to get all the data analysis and reports done.
I say used to, but still do. Even 10 years later me and my girlfriend (that studied at UiO) still tease each other about who is the smartest or had the hardest courses, or she mocks my ring, heh.