Easter dating table

Every leap year has two dominical letters, one for January and February and the other for the remaining months. The church considers March 21 to be the perennial date of the vernal equinox, but the real astronomical equinox can occur as early as March 19 (as will happen in 2096).Also, the moon does not slavishly follow ecclesiastical conventions.The mathematical principle here is that the length of a cycle is equal to the lowest common multiple of the lengths of its constituent subcycles (76 is the lowest common multiple of 19 and 4).

O’Beirne’s method puts the various cycles and adjustments into an arithmetical scheme.It was a tidy system, but unfortunately it did not accurately account for the true lengths of the lunar month and solar year.As the centuries passed, the calendar started to slip relative to the seasons.In 1990 Alan Mackay, a crystallographer at the University of London, realized that this near-regular slippage ought to show up in a graph that compared the date of Easter with the number of the year.The result is approximately a regular lattice, like the arrangement of atoms in a crystal.

Leave a Reply