[Voice]
[Yeah she's listened to you do this several days now and your condescending attitude bothers her a fair bit. But still she's replying anyway, for some reason.]
Well, at their roots, holidays were originally "Holy days." It rather depends on each religion how many holidays there are, though. Even with national holidays, Sentience doesn't announce all of them as it is, or maybe they just don't line up in all the dimensions it watches. There's quite a number of U.S. holidays passed by here as well - MLK Day, Groundhog Day, Presidents Day. The Children's Day a few days ago is usually celebrated June 1st too, isn't it?
We could soon just as well celebrate the Passover and César Chávez Day as likely as Lent or Mother's Day. Or maybe next week it'll be Rosh Hashanah and Beltaine.