I haven’t been to Japan, (I changed flights at Narita Airport once and that’s about it) but I’ve heard that. Bikkuri, you probably have some intel on this?
Yes, there is a holiday celebration for Christmas and New Years, but not the same as ours.
Christmas is close to the real Christmas, but mainly for romantic couples to go out (and to the love hotel).. On the outside (bubble) it DOES look the same, same decorations (and some of their own), cake, etc (case-by-case, it can be a family get together).
New Years is also similar (and case-by-case). Couples stay up, in line go through to shrines (or temples, can’t remember which) until midnight, then go to find a love hotel... Both are usually drunk by then.. lol
I am sure it hasn’t changed too much.
Christmas, especially, is all about business ($$$).
I believe, after they surrendered, with all of the troops stationed there, they picked up many of our habits and adapted more to their culture or benefit.