Hogwarts term finished on 15th December. Arthur and Molly go to visit Charlie in Romania, leaving their younger children to stay at Hogwarts. Harry invites them back to stay with him and James for the holidays. (I’m assuming Percy would rather stay at school and work but the twins, Ron and Ginny would all go.) No-one needs to make Polyjuice and/or accidentally turn into a semi-cat because there aren’t any attacks for them to suspect Draco of.
Thursday 21st is the Winter solstice. Thursday 21st is Yule. Sunday 24th is Christmas eve. Monday 25th is Christmas Day. Tuesday 26th is Boxing Day.
(December birthdays: finished)
2013
Hogwarts and Phoenix school of Magic both finished on 15th December. Phoenix school had their end of term feast on Friday 15th, Hogwarts has theirs on Saturday 16th.
Sunday 17th was the full moon.
Thursday 21st is the Winter solstice. Thursday 21st is Yule. Sunday 24th is Christmas eve. Monday 25th is Christmas Day. Tuesday 26th is Boxing Day.