It's called 'Ubisoft Weekend' and what it means for you is a whole heap of reduced prices on games. Ubisoft has practically put its whole library on sale.
And yeah, all the Assassin's Creed games as well are reduced, in addition to every other game Ubisoft has ever released on PC. Pretty awesome little sale.
It runs over the weekend, so plenty of time to peruse and make your choices.