Some folks wonder why Christmas is on December 25th given there is absolutely no clue in the bible, so here’s a handy passage from Professor Ron Hutton’s (( Wikipedia entry )) excellent book “The Stations of the Sun” quoting the Scriptor Syrus, a Christian writer in the late 300’s CE:
It was a custom of the pagans to celebrate on the same 25 December the birthday of the Sun, at which they kindled lights in token of festivity. In these solemnities and revelries the Christians also took part. Accordingly when the doctors of the Church perceived that the Christians had a leaning to this festival, they took counsel and resolved that the true Nativity should be solemnized on that day
Now 354 CE is the earliest calendar (that of Philocalus) which gives that date, but Prof. Hutton goes on to point out that the pagan festival that Syrus mentions was just 80 years old then, hardly an ancient practice. He says:
It had apparently been decreed only in 274 CE, by the emperor Aurelian, as a major holy day of a new and syncretic state cult with the sun as its official chief deity.
This in turn was built upon the older Syrian “Unconquered Sun” cult, which had its major festival in late summer. I suppose that last bit makes it almost appropriate for Australia. 🙂