What is the meaning of the lunar, lunisolar, solar and Gregorian calendars how are they differentiated?

The lunar, lunisolar, solar and Gregorian calendars are four different calendar systems that are differentiated for better understanding and application. First of all, the solar calendar, or the Gregorian calendar as we often call it, is a modern, internationally recognized calendar system based on the Earth's cycle around the sun and is used to mark the dates of daily life, such as going to school, going to work, and so on. The Gregorian calendar uses 365 days per year as the basic unit of calculation, with a fixed number of days in each month, e.g. January has 31 days and February has 28 or 29 days (in leap years).

In contrast, the lunar calendar, or lunisolar calendar, is the traditional calendar of China and some East Asian regions, and is usually closely tied to traditional Chinese festivals and holidays. The Lunar Calendar is not equivalent to the Lunar Calendar, although it also makes reference to the moon's cycle of waxing and waning, known as the lunar month, while taking into account the influence of the solar year to ensure correspondence with the agricultural seasons. The number of days in a lunar year usually ranges from 29.5 to 30.5, and the length of the months is variable, with some months having 30 days and others 29, hence the phenomenon of leap months.

In general, the solar calendar focuses on the solar year, while the lunar calendar combines lunar and solar cycles and has strong astronomical and agro-cultural connotations. Understanding and differentiating between these calendars helps us to properly understand and use dates in our daily lives, especially when it comes to traditional festivals and agricultural activities.