Why is Qingming Festival always on April 4th or 5th? Why is Qingming Festival on the Gregorian calendar?

Qingming is one of the 24 solar terms. Many people think that Qingming Festival is on April 5th. In fact, Qingming Festival fluctuates between April 4th and 6th. For example, this year's Qingming Festival is on April 4th. So, why is Qingming Festival always around April 5th?

Why is Qingming Festival always on April 4th or 5th?

There are 24 solar terms in the Chinese lunar calendar. Each solar term or middle term is defined as every 15 degrees that the sun moves on the ecliptic. Each solar term has a specific time, but in the Gregorian calendar, it is not fixed to a certain date. The time it takes for the Earth to orbit the sun is called the "tropical year" or "solar year", and the path of the sun against the background of the starry sky is called the "ecliptic". The actual length of a tropical year is 365.2422 days, while the length of a calendar year is 365 days. Therefore, there is an extra 0.2422 day (approximately 5.8 hours) every year, and the specific time of the solar term will also be "delayed" by 0.2422 days each year. In this way, after 4 years, the cumulative length is 0.9688 days, which is close to one day. In order to correct it, the "leap year" system is introduced in the Gregorian calendar, and an extra day, February 29, is added every four years. The extension of the solar terms sometimes causes the time of a certain solar term to pass midnight and reach the next day, or the solar term time is advanced by one day due to a leap year, thus causing the solar term time to change. Of course, no matter how it changes, the difference in the dates of the solar terms will only be within 3 days. The date of Qingming Festival will only change between April 4, April 5 and April 6.

Why is Qingming Festival on the Gregorian calendar?

Qingming Festival is an important traditional festival in our country and has a very important status. However, careful friends will find that although Qingming Festival is a traditional festival in our country, it is calculated according to the Gregorian calendar. So why is Qingming Festival calculated according to the Gregorian calendar, and why not the lunar calendar?

Qingming is one of the 24 solar terms in my country. Since the 24 solar terms relatively objectively reflect the changes in temperature, rainfall, phenology, etc. throughout the year, the ancient working people used it to arrange agricultural activities. "Huainanzi?Astronomy Instructions" says: "Fifteen days after the vernal equinox, when the Big Dipper points to Yi, the Qingming wind arrives." According to "Sui Shi Baiwen": "At this time, all things grow clean and bright. So it is called Qingming." When Qingming arrives, the temperature rises and the rainfall increases. It is a good time for spring ploughing and planting. Hence, there are agricultural proverbs such as “Plant melons and beans around the Qingming Festival” and “The best time to plant trees is during the Qingming Festival”. It can be seen that this solar term is closely related to agricultural production. Unlike other traditional Chinese festivals that use the lunar calendar, the Qingming Festival is actually a solar calendar date, fixed between April 4 and April 6 of the Gregorian calendar every year. Therefore, it is wrong to ask what day of the lunar calendar Qingming Festival is. The lunar calendar date of Qingming Festival is different every year. It is the Gregorian calendar date when the sun reaches a specific position. For example, this year's Qingming Festival is on April 4, 2016, which has nothing to do with the lunar calendar.

How to determine the date of Qingming Festival

The earth revolves around the sun once in 360 degrees of ecliptic longitude. When the earth reaches zero degrees of ecliptic longitude, it is the vernal equinox. Thereafter, there is a solar term every 15 degrees, for a total of 24 solar terms. Therefore, the dates of the solar terms in the Gregorian calendar are fixed, and due to leap years, they may differ by a maximum of two days. The lunar calendar is a lunisolar calendar that reflects phenological changes and guides farming time. It also combines the lunar calendar - the 29.5-day cycle of the moon phases (the time interval from one full moon to the next full moon). There are 12 months in a year, but each month has 30 basic days, which is bound to be different. According to the Gregorian calendar, Qingming Festival can be fixed on April 5 or 4 (depending on whether it is the 29th day of February in that year). From an astronomical perspective, when the apparent sun (the apparent sun is the position of the sun on the ecliptic) reaches 15 degrees of ecliptic longitude on April 5 or 6, it can be designated as Qingming Festival. The lunar calendar is a lunar calendar that uses the cycle of the moon phases to tell time. The interval from one full moon to the next full moon is one month; Yang refers to the sun. The Gregorian calendar, also known as the solar calendar, is based on the period of the Earth's revolution around the sun as one year.

What are the customs of Qingming Festival?

There are a series of customs during the Qingming Festival, such as tomb sweeping, outing, swinging, kicking football, etc. In addition, there are also some interesting "food customs" in eating. For example, in some places, eating eggs during Qingming Festival means having good health for the whole year; in the Jiangnan area, there is a custom of eating Qingtuan (green rice dumplings); in all parts of my country, a crispy fried food called "Sanzi" is loved by people; at the same time, Qingming Festival is the best time to eat snails, because the snails at this time have not yet reproduced and are the plumpest and fattest, hence the saying "Qingming snails are worth a goose"; in addition, different regions also have the customs of eating runbing, Wuren rice, zitui steamed buns, steamed noodle swallows, etc.; in some areas, there are also customs of eating cakes, Qingming fruit, sandwich cakes, Qingming rice dumplings, steamed rice cakes, Qingming cakes, and dry porridge during the Qingming Festival.