why is xmas on 25th december

Well, that's a good question! Christmas has been celebrated on December 25th for many centuries, and the exact origins of the date are a bit of a mystery. It's believed that the date was chosen because it coincides with the winter solstice, the shortest day of the year, and the beginning of the astronomical new year. This made it a natural choice for a holiday that celebrates the rebirth of the sun and the return of longer days. Additionally, it was also believed to be the day Jesus was born, so it was chosen to coincide with that as well.