YUMO hopes everyone have a good day in The National Day and the Mid Autumn Festival

   The Mid Autumn Festival in 2020 is very special, because the Mid Autumn Festival and the National Day in 2020 are actually the same day, which is a rare situation. Many people say it's a special feeling. At the same time, some people are curious. How long does the Mid Autumn Festival and national day appear on the same day? Why is that? 

    The Mid Autumn Festival and the National Day are on the same day, about once in 19 years. The next Mid Autumn Festival is on the National Day in 2020, then in 2031, the last in 2001 and the last in 1982. Because the Mid Autumn Festival is calculated according to the lunar calendar, while the National Day is calculated according to the Gregorian calendar, the days in the Gregorian calendar and the lunar calendar are different. 

    Zhao Zhiheng, President of the Tianjin astronomical society, said that the Chinese lunar calendar has 30 days of the big moon, 29 days of the small moon, and 354 or 355 days of the 12 months of the year, 11 days less than that of the tropical years. Four years later, it was less than a month. With the passage of time, there will be a strange disordered timing and timing phenomenon. To solve this problem, "leap month" has been added. This year's leap month appeared in June. 

    Not only did the Chinese Valentine's day be postponed, but also the Mid Autumn Festival went wrong. In addition, the Mid Autumn Festival generally occurs between September 7 and October 6 in the Gregorian calendar, which leads to the calendar phenomenon that the mid autumn festival meets the national day. If the leap months of the lunar calendar increase before August, most of them will lead to the Mid Autumn Festival, Zhao Zhiheng said. Why are there coincidences in 19 years? The number of days per month in the lunar calendar is determined according to the cycle of the moon. In fact, the average number of days per month is 29.5306. If multiplied by 12, there are only 354.3672 days in a year; the earth rotates 365.2422 days around the sun, so the actual number of days in the lunar calendar year is 10.875 days less than that in the Gregorian calendar, almost 11 days less in the Gregorian calendar, and 209 days less in the 19 years. 209 days divided by 30 is 6.9666, which means that in 19 years, the lunar calendar is almost seven months shorter than the solar calendar. In order to make the difference between the lunar calendar and the solar calendar not too big, it is necessary to make up for these seven months.

    In fact, the Chinese lunar calendar is a typical lunar calendar - it is formulated by considering the period of the moon's motion around the earth and the earth's period around the sun. It is a combination of the lunar calendar and the solar calendar. In order to make up for these seven months, people adopt the method of setting leap months in the 19 years of the lunar calendar - 19 years and seven leap years, that is, in the 19 years of the lunar calendar, 12 years are normal years, and there are 12 months in every normal year; adding 7 leap years (respectively the 3rd, 5th, 8th, 11th, 14th, 17th and 19th year), each leap year has 13 months. In this way, the number of days in 19 solar years is almost equal to the number of days in 19 lunar years. Therefore, every 19 or 19 birthdays, the Gregorian birthday and the Lunar birthday will have a chance to appear on the same day.