Leap year and leap month is a little common sense in our life. When we were young, we all learned how to judge leap year and the algorithm of leap year, but I believe many people forget the algorithm of leap year when they grow up. So is 2019 a leap year? Is there a leap month? This article will introduce what is a leap year, what is a leap month, and the algorithm of leap year. Let's have a look.
Q: is 2019 a leap year and is there a leap month in 2019?
A: 2019 is not a leap year. Generally, the year that can be divided by 4 is a leap year, and the year that cannot be divided by 4 is a normal year; When century years (that is, a hundred years) are encountered, only a leap year can be divided by 400, otherwise it is a normal year. Therefore, 2019 cannot be divided by 4, so 2019 is not a leap year, it is a normal year, and there is no leap month.
leap year
The so-called leap year was invented by the ancients in order to make up for the time difference between the annual days stipulated by the human calendar and the actual revolution cycle of the earth. The year that makes up the time difference is called leap year, including the year with leap day in the Gregorian calendar (Gregorian calendar) or summer calendar and the year with leap month in the Chinese lunar calendar.
Leap year phenomenon, that is, because the earth's cycle around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365.24219 days), that is, a regression year, while the normal year of the Gregorian calendar has only 365 days, which is about 0.2422 days shorter than the regression year. The remaining time is about one day accumulated every four years. Therefore, one day is added at the end of February in the fourth year, so that the calendar year length of the current year is 366 days. This year is a leap year.
In the current Gregorian calendar, there are 97 leap years every 400 years. According to a leap year every four years, the average additional 0.0078 days per year will be calculated. In this way, about 3 more days will be calculated after 400 years. Therefore, three leap years are reduced every 400 years. Therefore, the Gregorian calendar stipulates that when the year is a hundred, it must be a multiple of 400 to be a leap year; A year that is not a multiple of 400, even a multiple of 4 is not a leap year, which is the law of 'leap every four years, no leap every 100 years, and leap every 400 years'.
leap month
Leap month refers to a phenomenon in the yin-yang calendar. The yin-yang calendar arranges the big month and the small month according to the round or short of the moon, that is, the new moon. The length of a new moon is 29.5306 days, which is the cycle of lunar phase profit and loss. The yin-yang calendar stipulates that the big month is 30 days and the small month is 29 days, so the 12 months of the year are 354 days in total. The months of the yin-yang calendar have no seasonal significance. In this way, the 12 new moon constitute the Han calendar year, The length is 29.5306 & times; 12 = 354.3672 days, 10.88 days less than 365.2422 days in the regression year (i.e. nearly 11 days), and 0.91 days less per month (nearly 1 day).
There is a difference of 11 days between a year and a year in the Gregorian calendar. After only 17 years, the dates of the Yin and Yang calendar will be inverted in the same season. For example, a new year is spent in the snow. After 17 years, it will be necessary to fan the new year. Using such a calendar is naturally unable to meet the needs of agricultural production. Therefore, since the Qin and Han Dynasties, China's Yin Yang calendar has been parallel to the 24 solar terms, which are used to guide agricultural production.
And the ancients found that if the lunar year was changed to 13 new moons, the length was 29.5306 & times; 13 = 383.8978 days, which is more than 18 days more than the year of return. If the calendar is formulated according to the above provisions, there will be a strange phenomenon that the time of the day is inconsistent with the calendar and the time sequence is disordered and reversed. It is the so-called more or less. This is a contradiction.
In order to overcome this shortcoming, our ancestors found the method of "leap month" on the basis of astronomical observation, so as to ensure that the first month to march of the lunar year is spring, April to June is summer, July to September is autumn, and October to December is winter. At the same time, it also ensures that the beginning of the lunar year is at the end of winter and the beginning of spring.