I mentioned a little while back that the 50 days following Pesach are the weeks of the Omer. They end tonight with the holiday of Shavuot (literally, "seven weeks"). "50 days" translates to Pentecost in Greek, which is what Greek-speaking Jews (and by extension, the early Christian community) called this holiday.
Like many ancient holidays, Jewish and otherwise, Shavuot/Pentecost stems from the progression of the agricultural year, but long ago acquired religious significance as well. In this case, it marks the end of the grain harvest which traditionally occupies seven weeks in the late spring. Pesach marks the start of this harvest, and it thus became associated with bread and the story of the Passover. In like fashion, Shavout commemorates the giving of the Torah to the Israelites and the promise of a land of milk and honey. It is therefore traditional to eat bread and cheesecake before staying up all night to read Torah.
I have not yet been offered any cheesecake, but the night is young. If I have to stay up all night reading Torah to get sweets, though, I might just pass. Trying to read Hebrew for that long would undoubtedly give me a headache.