Christmas
The Dickensian Christmas is pretty close to how a Regency Christmas was, since Dickens was born early in the Regency period. There are no trees or stockings in A Christmas Carol, just lots of food, dancing, Christmas carols, and party games as well as greenery. Much of what we think of as an English Christmas did not come into being until the Victorian age. Christmas trees come from Germany, and the Dutch brought Sinterklaus to America long before Santa ever showed up in London.
That’s true of stockings as well, which is why I showed them as an anomaly in ’Twas the Night After Christmas (set in 1826). After Lady Devonmont reads the American poem “A Visit from St. Nicholas” (aka “’Twas the Night Before Christmas”), she decides it would be great fun to make stockings. But the custom of hanging them was practiced in America long before it started being practiced in England, because it was brought there by Dutch and German immigrants. The first reference I can find to it in England is in 1854. Eventually it became a big part of a Victorian Christmas.