Is there a difference between the imperial calendar and the lunar calendar?

Lunar calendar is a traditional calendar adopted by China, also known as summer calendar, middle calendar and old calendar. Some people call it the lunar calendar. It uses the strict lunar cycle to determine the month, and sets the leap month to make the average length of a year close to the tropic year, which has the attributes of lunar month and solar year, so it is essentially a kind of yin-yang calendar. In the lunar calendar, the date when the sun and the moon meet (the ecliptic is equal) is the first day of the month, that is, the first day. The average length of the first month of the lunar calendar is about 29.53059 days, so some months are 30th. Call the moon big; Some months are the 29th, called abortion. The date of the beginning of the month is calculated according to the position of the sun and the moon, not mechanically arranged. The lunar calendar takes1February as a year, ***354 or 355 days, which is different from the tropic year 1 1 day. Therefore, coordination is achieved by inserting 7 leap months every 19 years. The arrangement of leap month is determined by the 24 solar terms. The twenty-four solar terms of the lunar calendar include: beginning of spring, rain, fright, vernal equinox, Qingming and Grain Rain; Long summer, xiaoman, mangzhong, summer solstice, summer heat, summer heat; Beginning of autumn, first ripe, white dew, autumnal equinox, cold dew, early autumn frost; Beginning of winter, light snow, heavy snow, winter solstice, slight cold, cold winter.

The lunar calendar is not only designated according to the time spent in the year of the return of the earth, but also according to the changes of the moon phases, and it is more practical with reference to the surrounding meteorological and phenological conditions and agricultural activities, so it has become a calendar with four distinct seasons and easy memory. In China, the lunar calendar is especially suitable for the vast areas of the Central Plains.

"Imperial Calendar" belongs to the "official" almanac. The importance of almanac in social life is self-evident, and emperors of all dynasties attached great importance to the issuance of calendars. Since the Tang Dynasty, various dynasties began to strictly manage calendars. In the ninth year of Daiwa in Tang Wenzong (835), the King of Tang ordered the compilation of the first block-printed almanac "Xuan Ming Calendar". The sun, moon, time and festivals are recorded in detail in the Xuan Ming calendar. At that time, in order to prevent people from printing almanac indiscriminately, Tang Wenzong ordered that almanac must be examined and approved by the emperor himself and formally printed. Since then, the almanac has been called the "imperial calendar".

About the origin of the word "Imperial Calendar", some people say that it has something to do with Song Taizong. Said that whenever the end of the year, Song Taizong will send an almanac to civil and military officials and members of the royal family. This almanac is engraved with the dates and festivals of the lunar calendar, as well as the common sense of agriculture and planting. Because the almanac was given by the emperor, it is called "imperial almanac". It is certainly a great honor to get the almanac presented by the emperor, which many people expect. Influenced by it, the people gradually called the almanac "the imperial calendar".

The calendar recorded in the Imperial Calendar is generally limited to one year, and it changes in the second year. It would be wrong to look at this year's calendar with last year's "imperial calendar". So people often use the "old imperial calendar" to describe those conservative and outdated ideologies.