Question:
My Hebrew birthday is 17 Tevet, which this year falls on December 25th, a major non-Jewish holiday on which we usually refrain from celebrating or studying Torah. May I celebrate my birthday and/or read Tehillim for the occasion?
Answer:
It is permitted to make a birthday party on the 25th of December, but it should be clear that the part is for YOUR birthday...
Regarding not learning, if it is your minhag not to learn on nital night, it is only from nightfall until midnight, so you can still say tehillim the rest of the the night and day.
Best Wishes