That's what started today (or last night, technically.)
Means no eating, drinking, intercourse, smoking, swearing, lieing or getting violent between sunrise and sunset (the last few being a given seeing as you're not supposed to do those anyways) a month long.
Sunset here, because it's summer, is late as anything, around 21:00 .. And sunrise is around 04:00. Which means 17 long hours of fasting.
It does improve self discipline, train will power and cleanse your body though, so it's not as horrible as it might sound. (Those who have never tried it seem to think it more scary than those who have; Practice makes perfect?)
*yawns* I need to make sure I try getting enough sleep though, been lacking that lately (again).