No date is given in the Bible (for the birth of Jesus), so why do we celebrate it on the 25th December? The early Christians certainly had many arguments as to when it should be celebrated. Also, the birth of Jesus probably didn't happen in the year 1 but slightly earlier, somewhere between 2 BCE/BC and 7 BCE/BC, possibly in 4 BCE/BC (there isn't a 0 - the years go from 1 BC/BCE to 1).

The first recorded date of Christmas being celebrated on December 25th was in 336, during the time of the Roman Emperor Constantine (he was the first Christian Roman Emperor). A few years later, Pope Julius I officially declared that the birth of Jesus would be celebrated on the 25th December.

A very early Christian tradition said that the day when Mary was told that she would have a very special baby, Jesus (called the Annunciation) was on March 25th - and it's still celebrated today on the 25th March. Nine months after the 25th March is the 25th December! March 25th was also the day some early Christians thought the world had been made, and also the day that Jesus died on when he was an adult. The date of March 25th was chosen because people had calculated that was the day on which Jesus died as an adult (the 14th of Nisan in the Jewish calendar) and they thought that Jesus was born and had died on the same day of the year.