In order to learn when the Son of GOD was really born you need to first know a little about Hebrewism/ at the time Judaism and YAHUAH/ GOD.  First YAHUAH is a GOD of order.  YAHUAH gave us seven yearly High Sabbaths/ Holidays.  Every major event that has happen coincides with one of these seven commanded High Sabbaths, a High Sabbath is different from the weekly Sabbath which occurs every seven days.  The YAHUAH commanded Yearly Sabbaths are: Passover, Feast of Unleavened Bread, Shavuot, Feast of Trumpets, Yom Kipper, Sukkot, and Shemini Azeret.  Once a year a Priest of the Temple goes into the Holy of Holies, this is behind a three foot thick curtain where the Ark of the Covenant is kept to burn incenses.  A year and a few days before the Messiah was born on this one day of the year Yom Kipper which is also known as The Day of Atonement.  On Yom Kipper they cast lots to determine who would go into the Holy of Holies to burn incenses and the lots fell to the priest Zacharias.  To verify this read, Luke 1:5  There was in the days of Herod, the king of Judaea, a certain priest named Zacharias, of the course of Abia: and his wife was of the daughters of Aaron, and her name was Elisabeth.  6 And they were both righteous before God, walking in all the commandments and ordinances of the Lord blameless.  7 And they had no child, because that Elisabeth was barren, and they both were now well stricken in years.  8 And it came to pass, that while he executed the priest's office before God in the order of his course,  9 According to the custom of the priest's office, his lot was to burn incense when he went into the temple of the Lord.  10 And the whole multitude of the people were praying without at the time of incense.  11 And there appeared unto him an angel of the Lord standing on the right side of the altar of incense.  12 And when Zacharias saw him, he was troubled, and fear fell upon him.  13 But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elisabeth shall bear thee a son, and thou shalt call his name John.  14 And thou shalt have joy and gladness; and many shall rejoice at his birth.  15 For he shall be great in the sight of the Lord, and shall drink neither wine nor strong drink; and he shall be filled with the Holy Ghost, even from his mother's womb.  16 And many of the children of Israel shall he turn to the Lord their God.  17 And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord.  18 And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years.  19 And the angel answering said unto him, I am Gabriel, that stand in the presence of God; and am sent to speak unto thee, and to shew thee these glad tidings.  20 And, behold, thou shalt be dumb, and not able to speak, until the day that these things shall be performed, because thou believest not my words, which shall be fulfilled in their season.  21 And the people waited for Zacharias, and marvelled that he tarried so long in the temple.  22 And when he came out, he could not speak unto them: and they perceived that he had seen a vision in the temple: for he beckoned unto them, and remained speechless.  23 And it came to pass, that, as soon as the days of his ministration were accomplished, he departed to his own house.  At this point you have to turn back to the ways and traditions of the Hebrews.  The priest do not leave the Temple that night or even the next day.  It takes a couple of days to get everything cleaned and get ready to go home.  Understand Zacharias was not a young man, he was actually quite old as was his wife Elisabeth.  Zacharias would then have to travel some distance either by riding a donkey or by walking.  When an old man walks all day when he gets home believe me he is not in a mood to have sex, maybe the next night.  So let’s do a little math so far, Yom Kipper, one day days of cleaning two days day of travel one day that totals three days.  One day of resting up, total now four days.  Now let’s say this old man was spry and Zacharias and Elisabeth has sex the next night this brings us to a total of five days.  So why is this so important?  Between Yom Kipper and the first day of Sukkot is ten days.  Now for some math, Elisabeth becomes pregnant with in a few days of Sukkot, oh these days are also called Feast of Tabernacles and Shemini Azeret is known as the Last Great Feast Day.  Now we all know that a Human pregnancy last about nine months plus or minus a few days.  In Luke 28 And the angel came in unto her, and said, Hail, thou that art highly favoured, the Lord is with thee: blessed art thou among women.  29 And when she saw him, she was troubled at his saying, and cast in her mind what manner of salutation this should be.  30 And the angel said unto her, Fear not, Mary: for thou hast found favour with God.  31 And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name YAHUSHUAH.  32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David:  33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.  34 Then said Mary unto the angel, How shall this be, seeing I know not a man?  35 And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God.  36 And, behold, thy cousin Elisabeth, she hath also conceived a son in her old age: and this is the sixth month with her, who was called barren.  37 For with God nothing shall be impossible.To get our time line correct we need to go to Matthew 1:19 – 25 19 Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily.  20 But while he thought on these things, behold, the angel of the Lord appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Ghost.  21 And she shall bring forth a son, and thou shalt call his name YAHUSHUAH: for he shall save his people from their sins.  22 Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying,  23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.  24 Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife:  25 And knew her not till she had brought forth her firstborn son: and he called his name Yahushuah.The events described in Matthew 1:19 did not take place in a hour or two this would span a time frame of over two months and closer to three months.  At this time Mary would have left to go visit her cousin Elizabeth.  Now we know that when Mary came into the house of Zacharias, Elizabeth was six months pregnant with John who became known as John the Baptist.  Mary was three months pregnant which would give Marry another six months to delivery date.  Let us do a little more math Elizabeth is six months and Mary has another six months to go, six months plus six months equal twelve months.  This we all know and understand.  Now we back up to Zacharias was in the Temple on Yom Kipper five or so days later Elizabeth conceived this is right at or on the first day of Sukkot.  Twelve months later puts us back at Sukkot again one year later.  This would place the birth of the Son of GOD, on the first day of Sukkot. Why would Mary have to be three months with child when she met Elizabeth.  Okay, if Mary was only a few days or a week or two that would put the delivery date in January.  No GOD commanded High Sabbaths in January.  Also and this is a big one in Luke 2  1 – 6  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.  In a community/ Country that their income comes from farming the King would not try to collect taxes in the winter or spring when the people would not have the money/ goods to pay the taxes rather they would tax these people in the fall at or at the end of the harvest.  Also we need to understand not only when taxes were collected but the weather.  In mid October through spring in Israel it is the rainy season and it gets cold.  When sheep get wet and cold they can get pneumonia and die.  Read Luke 2 8—11  8 And there were in the same country shepherds abiding in the field, keeping watch over their flock by night.  9 And, lo, the angel of the Lord came upon them, and the glory of the Lord shone round about them: and they were sore afraid.  10 And the angel said unto them, Fear not: for, behold, I bring you good tidings of great joy, which shall be to all people.  11 For unto you is born this day in the city of David a Saviour, which is Christ the Lord.  After mid October sheep are keep in shelters at night, which would mean that after mid October the shepherds would not be keeping watch over the flocks at night.