Jesus was not born on 25 December .... waaaaaaay back, nobody...

Jesus was not born on 25 December .... waaaaaaay back, nobody knew on which day of the year he was born and various suggested days were proposed over the years until eventually in AD 350 Pope Julius declared that 25 December was to be regarded as the day of Jesus' birth ... and that day has been accepted by most Christians ...

As for the year when he was born, it has been determined to be between 4 BC and 6 BC - as calculated with reference to the known date when King Herod died ... there was no BC/AD at that time ... years were marked in the Roman world according to their reckoning ... and it was only several hundred years after the time of Jesus that the BC/AD system was introduced with the "supposed" year of Jesus' birth being the base year ... however, due to computational errors, that supposed year was incorrect and subsequently the mistake had to accounted for and Jesus' birth year was pushed back to somewhere between 4 and 6BC