October 4, 1582: Pope Gregory XIII declared
the next day wouldn’t be the fifth.
It would be Friday, October 15, 1582.
Ten days from the Julian calendar gone.
And let’s call the new version Gregorian.
In the Pope’s defense, he was trying to fix the existing calendar which was 10 days out of sync with the seasons – but still, a Pope just zapping 10 days out of a year seems like a bit of a power grab. No birthday parties for those born October 5-14 that year.