I've been part of a French/German/Danish family since 1985.
The French, like the Germans, like the Danes all celebrate Christmas on Christmas eve.
Basically the day goes somewhat normally till about 4 or 5pm when they start busying themselves with dinner - the kind Brits would eat on the 25th. In France around 7pm they'd suddenly get up, get all formal, kiss you on both cheeks and wish you a happy Christmas, offer a gift and food and drink would be the order of the rest of the evening with the more religious family members nipping out for a church service mid-evening.
In Denmark, it is the other way round. You go about your business normally till you eat a lovely big meal early evening and thereafter you go through to the room with the tree and sing carols dancing round it and at the end of the songs, you receive your gifts. Then again church is involved for the religious.
This is not what I grew up with. In Scotland we worked Christmas eve, and still do, though we often got to go home at 2pm instead of 5pm. Religious neighbours went to a service at 11-30pm. Before going to bed you left out a glass of milk or whisky for Santa and a biscuit of carrot for Rudolph. When you woke up on Christmas day "Santa" had been. There were gifts under the tree. At lunch time relatives came round and gifts were exchanged, and finally a nice meal would be had at 4pm. Thereafter you collapsed full on the couch in front of the Wizard of Oz, while playing a board game!
Now, I know I am a heathen so I am not best placed to question religious things such as Christmas, but isn't Christmas meant to be a celebration of the birth of Jesus, and isn't his birthday chosen universally to 25th December? Now, my birthday is 4th of February. I get my presents on the 4th. My family drop by on the 4th. We have birthday dinner on the 4th, work permitting...
So here's my confession - for the last 23 Christmases I have wondered why the Europeans are so obsessed with making the eve of the birthday special but the birthday itself a bit of a nothing day. Can any of you foreigners out there explain that one to me? Why does Europe celebrate 'Christmas' on December 24th? Though who am I to complain - I now get two Christmases a year...