Great image from CalamitiesofNature.com – click on it for the full size and read the transcript below.

[Linus and Charlie Brown conversing on a stage.]

Charlie Brown: “Isn’t there anyone who knows what Christmas is all about?!”
Linus: “Sure I can tell you what Christmas is all about.”
Linus: “December 25th is associated with the birth of many pagan gods, including Mithra, Horus, Hercules, Zeus, and Sol Invictus. The Roman festival Saturnalia would also end around this time. Christianity imported many of these pagan myths and traditions into its own customs around 400 AD. / Today Christians express outrage that Christmas is losing its Christian roots. This is ironic since it was Christianity that first hijacked the holiday in the first place to make it easier to convert new followers. / Nevertheless, it is a wonderful opportunity to share our love with friends and family and commit acts of goodwill for those that are less fortunate. It is a time for children to revel in their innocence and wonder about the world, and adults to find their inner child.”
Linus: “That’s what Christmas is all about, Charlie Brown.”

Further Reading

When Was the First Christmas?
The Christmas HOAX: The Real ‘Reason for the Season’
The Star in the East and the Three Kings
Dionysus: Born of a Virgin on December 25th, Killed and Resurrected after Three Days
Attis: Born of a Virgin on December 25th, Crucified and Resurrected after Three Days
Born of a Virgin on December 25th: Horus, Sun God of Egypt
Born on December 25th (Christ in Egypt)