Every winter, a sixth of the world’s population, including more than one billion Chinese citizens, celebrate Chinese New Year. The 15-day festival, also known as Lunar New Year or the Spring Festival, kicks off on the second new moon after the winter solstice, or according to the Gregorian calendar in use since the 16th century, sometime between January 21st and February 19th. But Chinese New Year goes back a lot further than the 16th century, it’s based on the ancient Chinese calendar, which existed as early as the 14th century BC. Chinese New Year remains the country’s most important social and economic holiday.