In the 380's a Christian woman named Egeria, made a pilgrimage to Jerusalem, and kept a journal, where she noted that Christmas was celebrated on 6th January, Epiphany, from the Greek "to Reveal":-
http://www.aquinasan...ass/article/119
I doubt that we will ever know the birthday of Christ as i find even 6th January dubious and open to manipulation by Hermetic Philosophers:-
http://www.hermeticf...ermeticism.html
The Jews then and now use previous sunset as the start of the day, so i would look at previous sunset on 5th January in Bethlehem. If i was a Wise Man i could follow Sirius from Persia with the method of the Sun setting as Sirius rises to Bethlehem, however i would need to know date of birth before i set out on my journey.
That we don't know year of birth isn't applicable, Sirius rises as Sun sets for many years on 5th January during this era in Bethlehem, only becoming out of synch by precession much later, so don't read anything into the year i picked...it happened every year, astronomy graph on link below:-
http://2012forum.com...=4079&mode=view
Don't read too much into 6th January as Epiphany date could have been chosen very early on because of the Sirius alignment in Bethlehem!