It's the first one.

The Christmas that appears in this movie is a party held by Hogwarts to welcome new students. Everyone can bring their family and friends to participate in this grand festival.

In the Harry Potter film series, the Christmas plot appears in the first film, Harry Potter and the Philosopher's Stone.

Students decorated the hall with holly and mistletoe and enjoyed a sumptuous Christmas dinner including turkey, roast meat, gravy and lingonberry jam.

Students also participated in various Christmas activities, raffled off firecrackers and attended a Christmas dance.