Many religions whose holidays were formulated before the worldwide spread of the Gregorian calendar have been assigned to dates either according to their own internal religious calendar, or moon cycles, or otherwise.
Many religions whose holidays were formulated before the worldwide spread of the Gregorian calendar have been assigned to dates either according to their own internal religious calendar, or moon cycles, or otherwise. Even within Christianity, Easter is a movable feast and Christmas is celebrated according to the older Julian calendar instead of the Gregorian by some sects of the religion.