Although December 25th is the day that we celebrate the birth of our Lord, most Bible students understand that it is not the date on which Jesus was born. We should not be surprised that the Bible doesn't tell us the actual date, because nowhere in the Bible are we told to remember His birth. We are clearly told to remember His death, burial and resurrection, but not His birth. However, celebrating Jesus' birth is a good thing, because it brings to remembrance the sacrifice He made when He humbled himself and came to earth; when the Lord of Glory took on human flesh; when the King of kings entered into poverty. Although the Bible doesn't specifically tell us when Jesus was born, it does provide some "whispers" of when if might have been.
1. It was not likely to have occurred after October because the weather in Israel turns very cold -- too cold for the flocks to have been in the fields overnight.
"Now there were in the same country shepherds living out in the fields, keeping watch over their flock by night." (Luke 2:8)
2. It's also highly unlikely that the Romans would have issued a decree for a census in December. It would have required travel to their city of birth and the terrain of Judea would have been difficult, or even impassable, during winter months.
"And pray that your flight may not be in winter or on the Sabbath." (Matthew 24:20)
3. Jesus came to tabernacle (dwell) with us, so it further supports a September birth (or very early October) having taken place at the time of the Feast of Tabernacles.
"And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth." (John 1:14)
"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." (Matthew 1:23)
For these reasons, and more, most Bible students believe Jesus' birth to have been in September during the Feast of Tabernacles and at a time when the sheep would have been in the fields overnight and travel in Judea would have been possible.