Julian years are slightly longer than 235 lunar months, while nineteen Gregorian or Revised Julian years are slightly shorter. Therefore, as time goes on, the eastern and western dates will coincide less and less, and in a few hundred years the western Easter will always precede the eastern one. The common ground is that, since the Synod of Whitby in AD 664, all churches agree that the "full moon" shall be observed on the fourteenth day of the lunar month. From this, the definition of Easter is derived: EASTER-DAY, on which the rest depend, is always the First Sunday after the Eighteenth Day of Miri, and if the Eighteenth Day of Miri happens upon a Sunday, Easter-Day is the Sunday after. All of which holds until the year 2099 inclusive, after which, on account of adjustments made every three or four hundred years in the calendar used in the calculation (of which Miri is the third month) the reference to the "Eighteenth" day shall be replaced by a reference to the "Nineteenth" day, and so on. The date of the full moon is identified in the table below. Both the old (current western) and new (current eastern) methods are given, as they have been in the Breviary since 1582. To use the table: The date of Easter is found from numbers which are allotted to certain dates as indicated in the table. For any particular year, the number which is taken is the same as the remainder that is obtained when one is added to the year and the total divided by 19. If there is no remainder 19 is taken. If the number is in Group A, Easter falls on the Sunday following the date against which that number appears. If the number is in Group B, Easter falls on the Sunday of the week commencing with the date against which that number appears. If the number is in Group C, the date against which it appears is to be treated as a day of March, and Easter falls on the day after the Saturday following that date. Rules for updating the table The boundary between Group A and Group B is usually set between 18 and 19 April, but if there are numbers against both 18 and 19 April (as in the 21st century) it's set between 17 and 18 April. The boundary between Group B and Group