The origins of Christmas as a holiday can be traced back to the 4th century AD when the Roman Emperor Constantine declared December 25th as the official date of the birth of Jesus Christ. The early Christians believed this date to be the most likely time of year when Jesus was born, and they began to celebrate his birth with feasts and rituals. However, the custom of exchanging gifts during Christmas can be traced back even further to the pagan winter festivals of the ancient world, such as the Roman Saturnalia and the Norse Yule. Over time, these traditions merged and evolved into the modern holiday we know today.