The traditions we associate with Christmas have evolved over the centuries. Here are answers to five questions about these traditions, from the date we choose to celebrate to the origin of Santa.

1. Why do we celebrate on December 25th?

The Bible makes no mention of Jesus being born on December 25th and, as more than one historian has pointed out, why would shepherds be tending to their flock in the middle of winter? So why is that the day we celebrate? Well, either Christian holidays miraculously fall on the same days as pagan ones or the Christians have been crafty in converting pagan populations to religion by placing important Christian holidays on the same days as pagan ones. And people had been celebrating on December 25th (and the surrounding weeks) for centuries by the time Jesus showed up.

The Winter Solstice, falling on or around December 21st, was and is celebrated around the world as the beginning of the end of winter. It is the shortest day and longest night and its passing signifies that spring is on the way. In Scandinavian countries, they celebrated the solstice with a holiday called Yule last from the 21st until January and burned a Yule log the whole time.

In Rome, Saturnalia—a celebration of Saturn, the God of agriculture—lasted the entire end of the year and was marked by mass intoxication (a tradition your uncle still upholds to this day). In the middle of this, the Romans celebrated the birth of another God, Mithra (a child God), whose holiday celebrated the children of Rome.

When the Christianity became the official religion of Rome, there was no Christmas. It was not until the 4th century that Pope Julius I declared the birth of Jesus to be a holiday and picked December 25th as the celebration day. By the middle ages, most people celebrated the holiday we know as Christmas.

2. How did Americans come to love the holiday?

The American Christmas is, like most American holidays, a mishmash of Old World customs mixed with American inventions. While Christmas was celebrated in America from the time of the Jamestown settlement, our modern idea of the holiday didn't take root until the 19th century. The History Channel credits Washington Irving with getting the ball rolling. In 1819 he published The Sketchbook of Geoffrey Crayon, gent., an account of a Christmas celebration in which a rich family invites poor folk into their house to celebrate the holiday.

The problem (if you're so inclined to call it such) was that many of the activities described in Irving's work, such as crowning a Lord of Misrule, were entirely fictional. Nonetheless, Irving began to steer Christmas celebrations away from drunken debauchery and towards wholesome, charitable fun. Throughout the rest of the 19th century, Christmas gained popularity and Americans adopted old customs or invented new ones, such as Christmas tress, greeting cards, giving gifts and eating a whole roasted pig (or is that just my family?).

3. Who popularized Christmas trees?

Since time immortal, humans have been fascinated with the color green and plants that stay green through winter. Many ancient societies—from Romans to Vikings—would decorate their homes and temples with evergreens in the winter as a symbol of the returning growing season.

But the Christmas tree didn't get going until some intrepid German dragged home and decorated a tree in the 16th century. Legend has it that Martin Luther himself added lighted candles to his family's tree, starting the trend (and leading to countless fires through the years). In America, the Christmas tree didn't catch on until 1846 when the British royals, Queen Victoria and the German Prince Albert, were shown with a Christmas tree in a newspaper. Fashionable people in America mimicked the Royals and the tree thing spread outside of German enclaves in America. Ornaments, courtesy of Germany, and electric lights, courtesy of Thomas Edison's assistants, were added over the years and we haven't changed much since.

4. What's the deal with Santa Claus?

The jolly, red-suited man who sneaks into your home every year to leave you gifts hasn't always been so jolly. The real Saint Nick was a Turkish monk who lived in the 3rd century. He was known for being charitable and selfless, eventually becoming the patron saint of sailors and children. According to legend, he was a rich man thanks to an inheritance from his parents, but he gave it all away in the form of gifts to the less-fortunate. He eventually became the most popular saint in Europe and, through his alter ego, Santa Claus, remains so to this day. But how did a long-dead Turkish monk become a big, fat, reindeer-riding pole dweller?

The Dutch got the ball rolling be celebrating the saint—called Sinter Klaas—in New York in the late-18th century. Our old friend, Washington Irving, included the legend of Saint Nick in his seminal History of New-York as well, but at the turn of the 18th century, Saint Nick was still a rather obscure figure in America.

On December 23, 1823, though, a man named Clement Clarke Moore published a poem he had written for his daughters called "An Account of a Visit from St. Nicholas," better known now as "T'was the Night Before Christmas." Nobody knows how much of the poem Moore invented, but we do know that it was the spark that eventually lit the Santa fire (just hopefully not in the same fireplace he slips down on Christmas Eve). Many of the things we associate with Santa—a sleigh, reindeer, Christmas Eve visits—came from Moore's poem.

From 1863-1886, Thomas Nast's illustrations of Santa Claus appeared in Harper's Weekly—including a scene with Santa giving gifts to Union soldiers. Not much has changed since the second half of the 19th century: Santa still gets pulled in a sleigh by flying reindeer, he still wears the big red suit and he still sneaks down chimneys to drop off presents. Contrary to popular belief, the Coca-Cola company did not invent the modern Santa. They did, however, learn how to use his image to get parents to buy soda during winter.

5. Who invented Rudolph?

Santa did get one more friend in 1939. Robert May, a copywriter for the Montgomery Ward department store chain, wrote a little story about a 9th reindeer with a disturbing red nose for a booklet to give customers during the holiday season. Ten years later, May's brother would put the story to music, writing the lyrics and melody.

Streeter Seidell is the front page editor of CollegeHumor.com and a mental_floss contributor.