Introduction:I believe that many people celebrate two birthdays every year, with classmates, colleagues and friends, and with their families, and most of the time the two birthdays will not be on the same day. Why are there lunar and solar calendars?Is the lunar calendar a lunar calendar?In this column, the senior sister will take you to understand the calendar.
What is the Gregorian calendar?The solar calendar, as you can see from the name, should be related to the sun. Long ago, the ancients felt the cyclical change of the seasons and realized that this change was related to the sun, and the solar calendar is a calendar that reflects the cycle of the four seasons. Because the orbit of the earth's rotation and the orbit around the sun are not in the same plane and have a certain angle, when the earth turns to different positions around the sun, the position of the sun directly on the earth will change, resulting in the change of the four seasons, and the period of change is the time taken by the earth to revolve around the sun. 
The time it takes for the Earth to make one revolution around the Sun is about 3652422 days, the solar calendar is based on this time, arranging how many days in a year. Sometimes there are 365 days in a year, sometimes there are 366 days in a year. There are 12 months of the year, with 31 days in the month, 30 days in the month and 28 or 29 days in February. The month of February, which has 29 days, or 366 days in a year, is also known as a leap year, and there is a leap year every four years. Calculated as a leap year every four years, the total number of days in four years is 365 * 3 + 366 = 1461 days, with an average of 365 per year25 days, which is 365 more than the actual time for the Earth to circle the Sun2422 days more than 00078 days, so that after four hundred years, it will be counted more than 312 days, so 3 leap years should be subtracted from the 400 years, so that the average length of each year is closer to reality. This is why a normal year divisible by 4 is a leap year, but a whole hundred year must be a multiple of 400 to be a leap year. What is a lunar calendar?The lunar calendar is a calendar based on the cyclical changes of the moon. At a very early age, the ancients discovered that the moon would change in cycles, from the absence of the moon to the full moon, and then to the lack of the moon, and so on. The moon phase changes for a period of about 2953,059 days, so in the lunar calendar is divided into 6 big months and 6 small months, the big month has 30 days, the small month has 29 days, and the average month of the year is 295 days. Each month and the moon phase change cycle differ by 003059 days, so that after almost 32-33 months, that is, 2-3 years, there will be a difference of one day, so you need to add one day every few years to adjust. Therefore, in the lunar calendar, there are also common years and leap years, with 354 days in a common year and 355 days in a leap year. 
The first day of the lunar month is the time when the moon is missing, also known as the new moonAround the fifteenth day of each month, the moon is at its fullest, which is called Wang. A lunar month can reflect the moon's waxing and waning cycle well, while a solar month cannot reflect this cyclical change of the moon. Since there is also a relationship between the waxing and waning of the moon and the tides, the ancients often used the tides according to the lunar calendar, which was of great help to navigation and fishing. 
Attentive friends may find a problem, the lunar calendar has 354 or 355 days in a year, which is about 11 days different from the 365 or 366 days of a year in the solar calendar. The difference of 11 days per year, the difference of more than 1 month after 3 years, and the difference of half a year after about 16 years. We know that the solar calendar can accurately reflect the changes of the seasons, because there is a large time difference between the lunar calendar and the solar calendar, so the lunar calendar does not reflect the change of seasons well, so few countries use a pure lunar calendar. What is the lunar calendar?The lunar calendar also arranges the number of days in each month according to the changes in the phases of the moon, which is the same as the lunar calendar. As we mentioned above, the difference between the lunar calendar and the cycle of the four seasons is about 11 days, and in order to keep up with the rhythm of the four seasons, the ancients decided to artificially increase the length of the year. Of course, it is not to add a few days every year, but every 2 or 3 years, one month is added to the year, which is known as the leap month, and the year with the leap month is also called a leap year in the lunar calendar. With the addition of 7 leap months every 19 years, the average annual length can correspond well to the Gregorian calendar, which is why every 19 years, many people's Gregorian birthday and lunar birthday will be on the same day. On the basis of the lunar calendar, leap months are regularly added, which forms the lunar calendar in our country, which not only retains the characteristics of the lunar calendar - can reflect the changes of the moon phases, but also retains the characteristics of the solar calendar - can reflect the replacement of the four seasons, so the lunar calendar is actually a lunisolar calendar. The lunar calendar is developed on the basis of the lunar calendar, but it is not exactly the same as the lunar calendar. Here I would like to remind you that the leap year of the lunar calendar and the leap year of the solar calendar are not the same thing, for example, the lunar calendar 2017 has a leap June, so it is a leap year;But in the Gregorian calendar, 2017 is not a leap year, and the year 2017 has only 365 days in the Gregorian calendar. 
When it comes to the lunar calendar, we have to mention the crystallization of the wisdom of the ancient working people in our country and the representative work of the intangible cultural heritage of humanity - the 24 solar terms. The 24 solar terms are also part of the lunar calendar, because China's lunar calendar is developed on the basis of the lunar calendar, so it is easy to mistake the 24 solar terms and the lunar calendar. The 24 solar terms were summarized by the ancients by observing the periodic changes of the sun, recording the natural phenomena such as wind, frost, rain and snow when the sun is in different positions, as well as the growth and development laws of animals and plants. The 24 solar terms are also based on the earth's circle around the sun as a reincarnation, so it is closely related to the solar calendar and belongs to the solar calendar part of the lunar calendar. You can compare the calendar, from the solar calendar, the 24 solar terms of the year are basically fixed, at most a difference of one or two days. For example, the beginning of spring is basically around February 4, and the upcoming February 4, 2019 is the beginning of spring. 
It is worth mentioning that February 4, 2019 corresponds to the 30th month of the lunar calendar in 2018, that is, Chinese New Year's Eve, and February 4, 2020 corresponds to the 11th day of the first month of the lunar calendar in 2020, which means that the upcoming lunar calendar 2019 will not have a spring festival. In folklore, a year without the beginning of spring is called the "Year of the Widow". Since there is a "widow's year", then there must be a certain year with two spring solar terms, and a year with two spring festivals is called "double spring years". The year 2017 of the lunar calendar is the double spring year, and interested friends can turn the calendar. Now can you tell the difference between the gregorian calendar, the lunar calendar, and the lunar calendar?The solar calendar calculates the number of days in a year according to the sun, and the number of days in each month is artificially determined, and has nothing to do with the change of the moon. The lunar calendar determines the number of days in each month according to the changes of the moon, fixes the number of months in a year, and does not adjust the length of the year according to the sun. The lunar calendar, on the other hand, is a lunisolar calendar that determines the number of days in each month according to the changes of the moon, and at the same time adds a leap month every 2 to 3 years, so that the average length of each year matches the solar calendar.