Glad to see some are happy with their calendar now fuller...
{The Support article I'd seen about Calendar suggested each
country had its own version; or use info there to import one
from google or other sources had been an option of a sort.}
Not sure if all versions of the Calendar would show recent
additions, only those using iCloud; unless recent download
update. I've not checked my most-recent Mac calendar;
and my iPad Mini1.1 (iOS 9.3.3?) didn't show Easter, etc.
Noted there were listed iOS calendar apps, but didn't look.
Maybe from my iPhone -- to cruise through App Store?
I prefer analog mechanical automatic watches, and paper
calendars because they both work when power goes out.
Pay to have a vintage means to see when duh holidaze, is.
We've nearly always celebrated 'hoppy eatster' too.

A friend's retriever down the road a bit, a Lab who liked
to bring stuff back and also barked a lot. I renamed him
'Sir BarksAlot' ~ it stuck: He also arrived when called.
So hopefully those who don't use iCloud calendar across
their iOS and macOS devices, can get along with an App.
Perhaps Vatican has an App, with real Easter, Lent & etc?
I'm not buying it...!😎