When Exactly Was Jesus Born?

The short answer is that nobody knows exactly. The year that seems to have the most votes in favour of it is 6 BC. In any case the birth of the Lord must have been at least during or before 4 BC because that is the year of the death of Herod "The Great." Here is a timeline taken from Wikipedia the online Encyclopedia:

• c. 6 BC – Suggested birth (earliest)
• c. 5 BC – Herod the Great's death (earliest)
• c. 1 BC – Herod the Great's death (latest)
• c. 6 AD – Suggested birth (latest), Quirinius census
• c. 26/27 AD – Pontius Pilate appointed governor of Judea
• c. 27 AD – Suggested death (earliest)
• c. 36 AD – Suggested death (latest)
• c. 36/37 AD – Pilate removed from office

The consensus favours a date between 4 BC and 6 BC as the date of our Lord's birth. However, the exact date isn't really of that much importance. The fact of his birth, his life and work, his sacrifice and his resurrection are what really matter. The fact that he will soon return to fulfill his prayer, "Thy Kingdom come; Thy will be done in earth as it is in heaven" is of primary importance to us while speculation about the exact year of his birth, while of interest, is, relatively speaking, of little importance.

-knowyourbible.com