Congrats on the 00!
There are a lot of people who observe Advent, but probably not for the same reasons as it was originally intended. My sister and her family observe the Eastern Orthodox "Christmas season," which ends (I think) on Jan 6th.
That's not Eastern Orthodox, that's traditional Western custom. Christmas begins, not ends with Christmas Day; it ends January 5th, the evening of which is called Twelfthnight. January 6th is Epiphany, commemorating the arrival of the Magi (and more).
Eastern Orthodox Christmas is January 7th, I believe.