I believe the first mention of St Patrick’s day being on March is from the late seventh century ‘Lumeix calendar’.
In the year 700 the spring equinox is calculated as being on March 17th (“The History and Practice of Ancient Astronomy”, James Evans, 1998, p. 166). Therefore there is the possibility that when March March 17th became St Patrick’sday during a period when it was common for March 17th to be the spring Equinox.
The Book of Armagh records the 7th century Tirechan description of the four honors which all Irish church rendered to St Patrick. Starting with: “i. Sollempnitate dormitationis ejus honorai [debet] is medio veria per .iii. dies et .iii noctes omni bono cibo praeter carnem quasi Patricius venisset in vita in hostium”
"1. Festival to honor his slumber to [be] the truth through the 3 days and 3 nights in addition to all the good food as Patrick came to life in the flesh of the enemy"
That St Patrick’s day was a three day and three night festival reminds me of use of plural “May-Days” in the 8th Century “Senchus Mór” law tract of “Cain Lanamhna. The law tract describes the laws of marriage and describes a marriage as running from Beltaine to Beltaine. This could be coupled with the 12th century Mecsa Ulad description of Conchobar’s Comfhled (a yearly rital marriage to the kingdom) which lasted three days and nights. (Note: “Second Battle of Mag Tuired” which occurs at Beltaine and like the other invasion tales occurs over three days.)
On a Christian doctrine level the honors over three days and nights is similar to a Triduum. This would place St Patrick day (within Ireland) on a par of importance as with Easter and other high days.
Yet there is a better match with the Triduum of St Joseph’s Day (March 19th). According Wikipedia there is a greater number of Lent dispensation than St Patrick’s day. In Spain it seems that St Joseph’s Day is associated with fire-rituals related to the Spring Equinox. http://en.wikipedia.org/wiki/Falles
So is St Patrick’s Days the Irish equivalent to the Spanish St Joseph’s Day in regard to church and the spring equinox?
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