The day has finally come: Dec. 21, 2012. This is when the calendar created by the ancient Mayans finally comes to an end, prompting some superstitious believers around the world to think that the apocalypse will happen today.

The Mayans are a group of indigenous American ethnic groups currently living in what is now southern Mexico, Guatemala, Belize and the surrounding areas. Their theories of time are based on repetitive cycles that extend throughout history, and the numbers 13 and 20 were considered highly significant in the Mayan culture.

According to HowStuffWorks, which has a detailed breakdown of the Mayans’ entire culture, these numbers were important because 20 represented the number of fingers and toes on the human body and 13 represented its number of joints.

Despite this calendar system coming to an end, NASA has already declared that the world will not end on Dec. 21, 2012. Judging by the Mayans’ calculations, the so-called apocalypse was scheduled to occur during the winter solstice. This happens when the sun reaches its southern-most declination of -23.5 degrees, causing areas of the Earth that are 66.5 degrees north latitude to be plunged in darkness. Places below that line, however, will have 24 hours of daylight left.

While some believers may be preparing for this alleged doomsday, others have decided to poke fun at the concept. Check out some of the best End of the World memes that have made their way around the Internet.