The disagreements have been particularly about the determination of moon phases and the equinox, some still preferring astronomical observation from a certain location (usually Jerusalem, Alexandria, Rome or local), most others following nominal approximations of these in either the Hebrew, Julian or Gregorian calendar using different lookup tables and cycles in their algorithms. Deviations may also result from different definitions of the start of the "day", i.e. dusk, sunset, midnight, dawn or sunrise, and the decision whether the respective starts of astronomical spring, Paschal full moon and Easter Sunday may occur in a single day as long as they are observed in that order.