The days in which students are forced to go through extreme torture due to examination from faculty members who love to enjoy to see students work harder then they do at any given day. Usually held at the end of a semester, followed by partying and extreme drug abuse, which leads to mental retardation.
It's just one of those weeks that happens to give you HELL, it occurs twice a year, and it often induces extreme insomnia and makes one look like a student on crack.
See
Dooms Day