There is some inaccuracy in the above, not all deities were associated with 25th December and in the myths of Horus his birth wasn't on 21st December, he was born during the Epagomental days of the Egyptian Calendar, this was five days added to the 12th month, this sounds good until you realize that the 12th month and year start was in the Summer, link below:-
It was Emperor Aurelian who ruled between 270-275 hoping to unite all different religions that were in the Roman Empire that made 25th December a standard day to worship different gods, that inaccurate links needs to value, please scroll down link below to religious reform:-
Which is a confusing point, why is Sol Invictus on 25th December and not on 21st December being the Winter Solstice??
Originally when the Julian Calendar was made on 1st January 0045BC, the Winter Solstice was aligned to 25th December, and when the church got together at the First Council of Nicaea in Iznik, Turkey they found that it had slipped to 21st December, obviously the Vernal Equinox had slipped as well, roughly the Julian Calender gains 3 days in every 400 years, and this made it difficult to calcalate Easter.
Rather than correct the error, which wasn't that difficult, which was leaving out 3 leap days every 400 years, like King Canute they just stopped the date to 21st March, (which applied to the Winter Solstice in December as well,) and as you know Easter uses the first full Moon after the Vernal Equinox to calcalate Easter.
By 1582 the real Vernal Equinox was falling on 11th March, so ten days were taken out, but not for the full length of the Julian Calendar, the adjustment was only made up to 325AD and the First Council of Nicaea.
I know this is a small point but is why Sol Invictus doesn't correspond to the Winter Solstice.
Edited by monk 56, 15 September 2012 - 09:24 AM.