Today marks the "Year of the Dragon, Month of the Dragon, Day of the Dragon, and Hour of the Dragon"! How was this calculated?

Science Times reporter epic

The first "Year of the Dragon, Month of the Dragon, Day of the Dragon, and Hour of the Dragon" will be held from 7:00 to 9:00 on April 10, 2024! This is a hot news topic that has attracted the attention of netizens recently. How is the "Year of the Dragon, Month of the Dragon, Day of the Dragon, and Hour of the Dragon" calculated? Yang Fan, deputy director of the Ancient Astronomy Research Center of the Beijing Planetarium, said in an interview with the Popular Science Times reporter, "This is actually an interesting phenomenon formed by the conversion of the traditional Ganzhi calendar and the zodiac calendar."

The Ganzhi calendar is based on the "Ten Heavenly Stems" and the "Twelve Earthly Branches". The "Ten Heavenly Stems" refer to "Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui", and the "Twelve Earthly Branches" refer to "Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai".

How to match the Heavenly Stems and Earthly Branches? "It is to match the '10 Heavenly Stems' with the '12 Earthly Branches' in order." Yang Fan explained, for example, the first Heavenly Stems "甲" and the first Earthly Branch "子" are paired to form "甲子", the second Heavenly Stems "乙" and the second Earthly Branch "丑" are paired to form "乙丑", and so on. When the tenth Heavenly Stems "癸" and the tenth Earthly Branch "酉" are paired, the Heavenly Stems continue to start from "甲" and are paired with the eleventh Earthly Branch "戌" to form "甲戌", and so on. The least common multiple of 10 and 12 is 60, so when the sixtieth pairing is arranged, it happens that the last Heavenly Stems "癸" and the last Earthly Branch "亥" are paired to form "癸亥", completing a cycle. The next cycle starts again from "甲子".

Yang Fan introduced that the ancients also matched the twelve animals or zodiac signs with the twelve earthly branches, and the "dragon" corresponded to the "chen". If the twelve zodiac signs are used to record the years, there are five dragon years every sixty years.

As for the main method of recording days in ancient China, it is to first calculate the stem and branch of each winter solstice, and then arrange the calendar of the year according to the order of the stems and branches. In this way, there are 5 "dragon" days in every 60 days.

"The Chinese lunar calendar is also divided into 12 months, but this month is divided by the synodic month (the cycle of the moon's waxing and waning). Now we may be more familiar with using numbers to indicate the months." Yang Fan said that the ancients also matched the 12 earthly branches with the 12 months. More than 2,000 years ago, they determined that the eleventh month of the lunar calendar, which is the winter solstice, would be the month of Zi, and the next winter solstice would be the month of Zi again, and leap months would not be counted. Therefore, if the months match the zodiac signs, the third month of the lunar calendar would be the "Dragon Month".

"The ancients also divided a day and night into twelve hours, corresponding to the twelve Earthly Branches, and set midnight as the Zi hour. The Chen hour is 7 to 9 in the morning in modern time." Yang Fan further explained, using the order of the zodiac signs, the "Chen" hour is the "Dragon" hour.

If we convert it this way, this year is the Year of Jiachen. The third month of the lunar calendar is from April 9 to May 7, which is the month of Chen. April 10 is the day of Jiachen, April 22 is the day of Bingchen, and May 5 is the day of Wuchen. The hour of Chen is from 7 to 9 a.m. every day. Connecting "Chen" with "Dragon", this year will of course have three "Year of the Dragon, Month of the Dragon, Day of the Dragon, and Hour of the Dragon". "Although there is some coincidence in this conversion, why not have a good start in the Year of the Dragon!" Yang Fan said.