@Em The 24th has ~never been a full holiday. The 25th and 26th are full holidays, the 24th and 31st are half holidays.

It’s true that the gift-giving in Germany is traditionally on the 24th, though the church visits are ~late at night or on the 25th in the morning for those who can’t do late nights.

Idk how you’re counting “most of the world” part, even ignoring countries that celebrate January 6th – I know several countries where the 25th is proper Christmas, and 24th "just" the eve.