Easter Based Holidays Rules
Easter based Holidays Rules can be quite simple for lay diaries, where all one usually sets is the number of days/weeks a holidays occurs before/after Easter Sunday (Western or Orthodox). For example, Good Friday would be 2 days before Easter Sunday.
In the case of diaries containing liturgical elements, things can get a bit more complex. The reason is that liturgical diaries have 2 conflicting sets of Sundays. The ordinary Sundays are counted from the beginning of the year, while many important holidays related to Easter are counted counted backwards from the date of Easter Sunday. Depending on the date of Easter, some holidays, such as Ash Wednesday (46 days before Easter), will conflict with some of the ordinary Sundays. In those cases you will need to use Conflict Rules.
See also: Recurrence Rules Options.