For the first 3 centuries of Christianity’s existence, Jesus Christ’s birth wasn’t celebrated. When church officials settled on December 25 at the end of the third century, they likely wanted the date to coincide with existing pagan festivals honoring Saturn (the Roman god of agriculture) and Mithra (the Persian god of light). That way, it became easier to convince Rome’s pagan subjects to accept Christianity as the empire’s official religion.
I am Christian, but isn't strange that it's okay to observe Easter and Christmas, but SO many churches won't celebrate Halloween because it is an "evil pagan" holiday! But, history reveals that us "Holiday-observing Christians" aren't so "Christian" after all! We are just continuing to practice pagan traditions that Constantine simply slapped a Christian "sticker" on!