holy day

a consecrated day or religious festival, especially one other than Sunday.

Origin of holy day

see origin at holiday

One young fellow was calling out, "At least, it is a holy-day, and I shall go to Paris!"

Devereux, Complete |Edward Bulwer-Lytton
This day is kept strictly as a holy-day, being the King's Coronation.

Diary of Samuel Pepys, Complete |Samuel Pepys
The religious and moral duties to which the "holy-day," as it is called, should be strictly devoted are there specified.

The Beginners of a Nation |Edward Eggleston.
In pre-Reformation days, a holiday was a holy-day, when man went not forth to his labour.

Curious Church Customs |Various

In older missals they were extremely numerous, almost every Sunday and Holy-day having one assigned to it.

Encyclopaedia Britannica, 11th Edition, Volume 16, Slice 7 |Various

holy day

a day on which a religious festival is observed