Transcript:
Housemate: Question. Why is Friday evening the end of Friday but, Christmas Evening is the beginning of Christmas?
Me: Technically there are two. “Christmas eve” and “Christmas Eve”. That’s not counting the third one, where “Christmas” refers to the season instead of the day(s), meaning there are many Christmas eves but only one Christmas Eve.
Originally, Christmas Eve was regarded as the point in time where the 24th became the 25th, rather than the entirety of the 24th.
This is why there’s also a New Year’s Eve. December 31st is the evening prior to the new year. So was December 24th the evening prior to the religious mass (gathering) to celebrate Christ - Christmas.
Completely different from today, where Christmas starts on November 1st and continues until sometime in mid-February. :)