This is a question of utmost importance given the fact that today's world spends billions on gifts, travel and much fuss around this so called season of Yuletide. Many commitments involving time, and lots effort go into preparation for the supposed birthday of the Son of God.

The Bible is however strangely silent on the festival called Christmas and does not even deign to mention it by the said name. As for the day itself, December 25th, it is not mentioned. Not even once! Many scholars have persuasively argued, citing historical sources, that Christmas is in fact, indelibly etched with the mark of paganism both in its origins as well as its character. 

What then, does the Bible say in answer to the question of Yahshua's birth? 

In Luke 2:1 - 7, we see the Roman Emperor Augustus Caesar ordering a census to be taken in the entire Roman world:

[1]And it came to pass in those days, that there went out a decree from Caesar Augustus, that all the world should be taxed.

[2](And this taxing was first made when Cyrenius was governor of Syria.)

[3]And all went to be taxed, every one into his own city.

[4]And Joseph also went up from Galilee, out of the city of Nazareth, into Judaea, unto the city of David, which is called Bethlehem; (because he was of the house and lineage of David:)

[5]To be taxed with Mary his espoused wife, being great with child.

[6]And so it was, that, while they were there, the days were accomplished that she should be delivered.

[7]And she brought forth her firstborn son, and wrapped him in swaddling clothes, and laid him in a manger; because there was no room for them in the inn.

(Luke 2:1-7, KJV) 

Just as modern censuses are tied to a country's social-economic planning, so it was with Augustus' census. He was interested in taxation. This is very clear from the authorized version's account of the event. Taxation, in turn, was tied to the harvest in those early times when agriculture was the backbone of the economy (you tax the increase on someone's plenitude, mainly agricultural produce). Logic therefore would seem to suggest that a census would be conducted immediately after the harvest). Such a time would be far  removed from the depth of the northern hemisphere's winter!

Furthermore, in Luke 1:8 we learn that there were shepherds actually out in the fields tending their flocks by night! Again logic would seem to dictate that these shepherds could only do that during a season that was much warmer than a freezing winter.

Geographically speaking too, the sun is usually overhead the Tropic of Capricorn (in the Southern Hemisphere) on 22nd December! This would automatically mean that it is winter in the northern hemisphere! The body of evidence and logic would therefore seem to militate against December 25th as the date of Yahshua's birth. 

But then, if he was not born on December 25th, then when would have been the probable date for this ground shifting event? 

In Luke 1:5 we learn of the priest Zachariah of the PRIESTLY DIVISION OF ABIYAH. This is a very important fact given that priestly divisions set out who ministered and at what time (of the month) in the year during the Levitical Priesthood. The order of service was put in place by King David as we learn from 1Chronicles 24:1-3:

[1]Now these are the divisions of the sons of Aaron. The sons of Aaron; Nadab, and Abihu, Eleazar, and Ithamar.

[2]But Nadab and Abihu died before their father, and had no children: therefore Eleazar and Ithamar executed the priest's office.

[3]And David distributed them, both Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, according to their offices in their service.

(1 Chronicles 24:1-3, KJV) 

The Kohen Gadol Aaron had four sons: Nadab, Abihu, Eleazar and Ithamar. Nadab and Abihu died before the LORD for using unauthorized fire in sacrifice (Leviticus 10:1-3). Only Eleazar and Ithamar remained in the priestly service. Eleazar had 16 descendants, while Ithamar had 8, making a total of 24 priestly families. Since a year has 12 months, it therefore meant David had to assign (by lot) which family served at the altar in two week intervals (or shifts). In 1Chronicles 24:6-19, we are given a complete breakdown of how these priestly divisions were ranged throughout the year. 

It is from this rota that we learn that Zachariah went to minister in the Temple during the second part of the 4th month (since that was when Abiyah's Division came into duty). It was during such a time that Zachariah saw the Angel Gabriel in a vision as Luke reports (Luke 1:11-17). Afterwards, at the end of the month, he proceeded home and Elizabeth subsequently fell pregnant in fulfillment of Gabriel's words (Luke 1:23-24). Being an old lady well advanced in age, Elizabeth opted to go into seclusion for five during the said time (verse 24). 

It was on the sixth month of the said seclusion that Mary went to visit her cousin Elizabeth (Luke 1:26, 36-40). Now, counting from the seventh month of Elizabeth's pregnancy (as the beginning of Mary's pregnancy, since Luke 1:42 shows that Miryam had already conceived Yahshua), it is easy to establish that her pregnancy came to term during the seventh month of the Bible Calendar, that is, the month of Ethanim.In Gregorian Calendar terms, that date would be around late September or early October. This is a date that is quite far removed from the 25th December date! Kindly see the accompanying time chart outlining the order of events as per Luke's account. Blessings.