When the Dragon-Blooded overthrew the Solars and established the Shogunate, they created a new calendar. In parts of Creation where the Realm has little influence, such as Lookshy and the rest of the Scavenger Lands, this calendar remains in common use. E:TO does not specify, but presumably, the year uses the same month and weekday names as in the Realm, and starts/ends at Calibration.