Our organization is technically closed, but our department must be manned for year-end stuff. 

We each volunteer to come in for one day between Christmas and New Year's so that we have a skeleton crew on duty if anything hits.  These are usually "light" days, limited to covering the phones and opening the incoming mail. so we arrive "sometime before 9:30" and leave after the mail arrives, which is around 2PM.  We are also permitted to dress fairly casually on these days.

There's about 3-4 of us on each day and we all get along well, so it ends up being a fun day.  We bring in goodies, chat, play music.  I usually spend the day giving my desk a good cleaning and the files a good going over.