1. Valentine's Day started off as a kinky Roman sex holiday. DIsney / Via usca-potter.tumblr.com From Feb. 13–15, Romans celebrated the wild and crazy festival of Lupercalia, during which men would lightly whip women to make them fertile before spending the night with them. Early Christians tried to make this holiday more wholesome by naming it after two executed saints, both Valentine. It wasn't until Chaucer, though, that Valentine's Day became a holiday focused on romance instead of vigorous loving. 2. Christmas started off with gambling, feasting, and the return of the Unconquered Sun. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF United Feature Syndicate / Via retzam589.tumblr.com On Dec. 25, the Romans would celebrate the rebirth of the Unconquered Sun god, citing the start of longer days after the winter solstice. This celebration occurred closely after the holiday Saturnalia, during which Romans would have large feasts and give each other gifts. It wasn't until Christianity became the official religion of Rome that Christmas came to the forefront. 3. Halloween was all about bonfires and hiding from possessing spirits. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Touchstone Pictures Samhain marked the end of summer for the Celts, and the beginning of darker times. On this day divination was thought to be particularly powerful, and spirits entered the world seeking entertainment or bodies to possess. For this reason, people dressed up in disguises to avoid the malevolent spirits and danced around massive bonfires. As this area became Christian, the holiday became linked to All Soul's Day. 4. Purim is less "drunk Jewish Halloween" and more "Middle Eastern New Year." Flickr: matzuva Purim is traditionally a two-day-long festival in which Jews dress up, spin traditional noisemakers, and drink copious amounts of wine to celebrate their survival after an attempted genocide in ancient Persia. Originally, though, it is believed that Purim began as a traditional Babylonian new years celebration. The Jews enjoyed it immensely, and simply took the belief home with them to Israel. 5. Easter is a delicious mash-up of the best parts of other spring festivals. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Universal Pictures / Via weheartit.com Numerous cultures throughout the world would celebrate a festival, around the same time as Easter, based around the rebirth of the world after winter. The exchange of eggs was actually an old Middle Eastern tradition, while the Easter Bunny was based on the hare symbol of a Germanic goddess. 6. New Year's has stayed the same, except for it having been dedicated to a god. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF ABC Until Julius Caesar, new year's festivities were generally based on agricultural cycles. After Caesar took control of Rome, he instituted calendar reforms and made New Year's Day Jan. 1. This date was chosen because January was named after the two-faced Roman god Janus, who could see backward and forward in time. This date was celebrated by feasting, drinking, and sacrificing to Janus. 7. April Fool's Day possibly started as a joke at the expense of French peasants. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF NBC The origin's of April Fool's Day are shrouded in mystery, but the most popular theory goes like this: After the Gregorian calendar was accepted in France in the 1500s, the new year was changed from April 1 to Jan. 1. The news was slow to spread, or some refused to make the change, and the rest of society began to play jokes on those unfortunate few. 8. Mayday is less about folk dances and more about fertility and revolutionary socialism. Flickr: 75012107@N05 The original Mayday was celebrated in the British Isles as a fertility festival. People would erect a Maypole, dance around it, and whenever their ribbons would intertwine they were destined to get married. In 1886, socialists and anarchists clashed with police in Chicago while calling for an eight-hour workday. In honor of this event, May 1 was declared to be holiday for international workers. Today, Mayday celebrations are an odd mix of paganism and socialism from the unintentional combination of the two holidays. 9. Groundhog Day comes from an old, correct, German belief in the wisdom of hedgehogs. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Columbia Pictures Germans believed, possibly inspired by an older British theory, that if the sun shone on Candlemas Day, winter was only half over. They measured this by waiting to see if hedgehogs would cast a shadow — if they did, snow would continue until May. When German settlers came to Pennsylvania, they brought this belief with them, as well as deciding that a groundhogs could replace hedgehogs in a pinch. 10. Mardi Gras and Carnival are a possible mash-up of the most enjoyably sordid Roman sex festivals. Flickr: hasitha_tudugalle Mardi Gras and Carnival form the excess and debauchery leading up to the penitence of Lent. This flair possibly comes from the blending of the Roman holidays Lupercalia and Bacchanlia — which Rome actually outlawed due to how lewd it was — together by early Christians in an attempt to supersede the old pagan customs. 11. Labor Day was created as a failed campaign promise to win reelection. fabulous-trotskyist.tumblr.com In 1894, President Grover Cleveland hurriedly signed Labor Day into law in an attempt to win reelection. He was extremely unpopular after having used U.S. marshals to violently put down a series of railroad strikes throughout the country. Ultimately his gamble was unsuccessful; the bill was passed but he was not reelected. 12. Three moochy kids' codename for trying to find free weed started 4/20. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Columbia Pictures In 1971, three high school students in San Rafael, Calif., heard rumors of a free weed patch out by a lighthouse. They would meet everyday at 4:20 p.m. after finishing track practice, and smoke on the way to look for the marijuana. Overtime, 420 became code for smoking among the group. As chance would have it, the three knew the Grateful Dead, who used the term in their music, leading to it's unofficial holiday status today. 13. Friday the 13th is media-made bullshit. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF challenger23.tumblr.com Though Friday has often been held to be an unlucky day — with references to this going as far back as Chaucer — and the number 13 has been unlucky since early Christian times, Friday the 13th was not deemed unlucky until the 20th century. Stories of the Knights Templar being disbanded violently on a Friday the 13th are modern inventions, and the first reference to Friday the 13th doesn't come about until it showed up in newspapers in 1908.