Even before I stepped into IIM-A, I heard/read stories about 4 hour sleep, 1 hour notice surprise quizzes spoiling lunch and generally about the hectic first year schedule.
Considering that the academic curiculum is (broadly) same across all IIM's in the first year, why does only IIM-A have such a rushed culture? One part of the puzzle lies on our dedicated Profs who prepare hard for the classes even to the extent of sending class materials at 2am for the 8:45 lecture(I'm not making this up!). Seeing their dedication, no one has an excuse for ignorance when s(he) is cold-called. And the classroom time: study time(pre/post class) vastly varies across students but is atleast 1:2. Multiply that into nearly 4 hours classes and you see why people joke that the A in IIM-A stands for Acads.
The second part of the puzzle lies in the various clubs in IIM-A nearly 40 at last count. Fucchas(first years) enrol generally in 1-5 clubs and a good chunk of time goes there. And then assignments, WAC, dorm parties, recreations(Frisbee, soccer, cricket etc), hanging out at eateries is all non(academically)value added time-but which prepares you for life.
Thirdly, punctuality is non negotiable here. Deadlines are given to the last second so 11:00am deadline is 10:59:59 with even 1 second delay not condoned. This of course prepares the student for real life & to discard the "Indian standard time" he is used to. But it is also a major cause of the "pressure".
It is upto the individual. If he just focusses on acads, a pretty relaxed life will ensue. But then, the whole IIMA experience will not just accrue. A fine balance needs to be struck between work and leisure here.