It occurs to me that the pagan revivalists have the perfect holiday to celebrate this year on December 25th. If they do, they will owe it (sadly enough) to Zenobia.
In the year 274, the Emperor Aurelian inaugurated the feast of the Sun-god in Rome on the day of that god's birthday, that is, on the winter solstice, which falls on December 25th in the old Julian calendar. The god he had in mind was Sol Invictus, "the Unconquered Sun", but the god he had in hand was Bel-Helios of Palmyra. When the emperor had destroyed Zenobia's city the previous year, the eagle-bearers of the Third Legion Cyrenaica despoiled the Temple of Bel: Aurelian, we are told, removed from this temple the statue of Bel-Helios to a new home in Rome.
He built a temple for the new god on the eastern Campus Martius, today between the Via del Corso and the Piazza San Silvestro (so Bel may still be lurking under the church of San Silvestro in Capite). Something of this huge temple remained on the site until at least 1629 when Giovanni Battista Mercati made this haunting etching of its ruins.
Happy Birthday, Sun!
Aurelian established annual Games to honour the Sun's birthday and kicked off the event with 30 chariot races. We last hear of the Games of the Sun being celebrated in 354 AD. In that same year, coincidentally, the so-called Philoclian calendar (a list of the early bishops of Rome) mentions under the year 336, "25 Dec.: natus Christus in Betleem Judeae." The supreme god of the Empire had changed, but his birthday hadn't.
Updated 13 December 2011
On the question of Sol's precedence on December 25th, see now 'Whose Christmas Is It Anyway?'