Before switching to the Gregorian calendar officially in 1911, the Chinese had used a lunar calendar since time immemorial; and even today, the Chinese still celebrate their traditional festivals by the lunar calendar. In each lunar month, the first day (the new moon) and the 15th day (the full moon) are major events; and the 15th day of the first month (the Lantern Festival) and the 15th day of the eighth month (Mid-Autumn Festival, September 9th this year on the Gregorian calendar) are the largest celebrations besides the Lunar New Year and the Dragon Boat Festival.