Plenty of time for fun...nice big blocks of exams allow slack time...
and lecture schedule allow us to miss whatever class we want. I am one of the people who prefers to learn on my own as opposed to going to class...but class first year is like 9 or 10 to 12, then I think about 3 afternoons a week are filled up from about 1 to 4 or 5ish.
It's not as bad as it may look on paper. B/c in reality, you don't HAVE to go to every class and labs are usually out by 4 instead of 5... There are some small group sections, but that mainly becomes part of second year curriculum.
I'm down at midtown probably 4 times a week. First year I was down there a decent amount as well. PM me if you want a copy of second year schedule...and I think BEZ2 or something on here is a first year here at columbia...
I sometimes suck at being helpful with semi-vague questions...but hopefully someone else will come show you the light...
