How to understand the lunar calendar and Gregorian calendar?

A calendar of China in the lunar calendar, which is a kind of lunar calendar, is generally called lunar calendar. Normal year 12 months, 30 days in the big month, 29 days in the small month, and 354 or 355 days in the whole year (which month is big and which month is small in a year, which varies from year to year). Because the number of days in each year is about eleven days worse than that in the solar year, there are seven leap months in nineteen years, and there are 383 or 384 days in a year with leap months. According to the position of the sun, a solar year is divided into 24 solar terms to facilitate agricultural planting and other activities. The chronology is matched with heavenly stems and earthly branches, with a period of 60 years. According to legend, this calendar originated in the Xia Dynasty, so it is also called the Xia calendar. Also known as the old calendar.

Gregorian calendar is the current international calendar, also called solar calendar, commonly known as solar calendar. The solar calendar, also known as the solar calendar, is based on the fact that the earth orbits the sun once a year, which is very common in western countries, so it is also called the western calendar. Since the Revolution of 1911, China has adopted the solar calendar since the first year of the Republic of China, so it is also called the "national calendar". In order to be symmetrical with China's old calendar, it is also called "new calendar". 1949 officially stipulates the calendar year.

He was born in julian calendar BC 1582, and Pope Gregory XIII of Rome designated the second day of julian calendar 1582 10 year 10 day as Gregorian calendar 10 year/0 month/0/5 day. At the same time, julian calendar's leap rule was revised.

The earth's orbit around the sun is actually 365.24 19 days (solar year), which is 0.242 19 days less every year, 0.96876 days less every four years and 96.876 days less every 400 years. So 400 years needs 97 leap years. Leap year is the end of February plus one day, with 366 days in the whole year. It took 3333 years to get a day's error.

There are three kinds of years: the earth revolves around the sun for 365 days, 6 hours, 9 minutes and 9 seconds, which is called "sidereal year"; The year of perigee is called "perigee year", when the sun passes perigee and travels eastward along the ecliptic, and then passes perigee at 6: 13: 48 in 365 days. The sun crossed vernal equinox, followed the ecliptic to the east, and then crossed vernal equinox, which lasted for 365 days, 5 hours, 48 minutes and 46 seconds. It was called "the year of the Tropic of Cancer", also known as "the year at the end of the year".

Because the vernal equinox (vernal equinox and autumnal equinox) retrogrades westward along the ecliptic for about 50 seconds every year, the time of the return year is shorter than that of the sidereal year, with a difference of 20.23 seconds, which is called "precession". These three years are different. In order to keep the solar terms hot and cold every year, the tropic year is chosen as the Gregorian calendar year.

It is necessary to remember the time of the Tropic of Cancer. In order to facilitate memory, the formula of a song is compiled as follows:

How long does it take for the earth to orbit the sun for the first anniversary? Three, six, five hours, 48 minutes, 46 seconds.

1 month 1 day to the following year 1 month 1 day, which is called a year. Older people should be equal to the actual number of years. However, the number of days in a year must be an integer, so it is not convenient to count odd hours. Therefore, taking 365 days as a year, there are 5 hours, 48 minutes and 46 seconds left every year to about one day in four years. Therefore, one day is added every four years, which is called leap year.

A year without leap days is called an "average year", with 365 days in an average year and 366 days in a leap year. However, the four-year leap is only 23: 15 minutes and four seconds. There are too many leap days today. Over 44: 56 seconds, it accumulates to 25 leap, which is 17: 58 minutes and 24 seconds, which is about three quarters of a day. Therefore, a leap will be wasted every hundred years, and it will not be wasted until the 400th year. If we set a leap every four years and subtract three leap every 400 years, it will take eight 400 years, that is, 3200 years, to make up the difference of this day.