Why there are two days every day ... lunar calendar and solar calendar ... how easy it is to remember only one.

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 revolves around the sun once a year, which is very common in western countries, so it is also called the western calendar. China has been using the solar calendar since the Revolution of 1911, so it is also called the "national calendar".

The orbit of the moon is "lunar calendar", and the calendar based on the apparent motion law of the moon is called "lunar calendar" for short.

Lunar calendar is one of the traditional calendars in China, also known as lunar calendar, lunar calendar, ancient calendar, yellow calendar, summer calendar and old calendar. Because there are solar terms changes in the calendar, which are closely related to agricultural planting activities, the "Lunar Calendar" plays an important role in the lives of China people, especially farmers.

Because the lunar calendar does not consider the movement of the earth around the sun, there is no fixed time for the changes of the four seasons in the lunar calendar, which cannot reflect the seasons. This is a great shortcoming. In order to overcome this shortcoming, people later decided to adopt a compromise calendar, the so-called yin-yang calendar.