Are the 24 solar terms based on the lunar calendar or the solar calendar?

The 24 solar terms are divided according to the solar calendar.

Twenty-four solar terms are part of the traditional lunar calendar, which is essentially a solar calendar, and the general Gregorian calendar is also a solar calendar. The natural coincidence degree between them is high, but there is a fluctuation of 1-2 days.

The twenty-four solar terms are essentially 24 fixed positions of the sun's apparent motion on the ecliptic (the ecliptic is divided into 24 points, each of which is 15). Four of them are the most important: vernal equinox (longitude 0, day and night are equally divided), summer solstice (longitude 90, the shortest shadow and the longest day), autumn equinox (longitude 180, day and night are equally divided) and winter solstice (longitude 270, the longest shadow and the longest night).

After observing the bisection, you can calculate the rest of the solar terms. So the interval of each solar term is roughly 365/24= 15 days (in fact, the revolution of the earth is not uniform, so it is not a simple division). But solar terms are precise longitude, so solar terms are actually precise time, not a day. It just means that the solar term falls on a certain day, which is called the solar term.

The 24 Solar Terms

Twenty-four solar terms are special festivals in the calendar to express natural rhythm changes and establish "December construction". A year is divided into four seasons, three months in spring, summer, autumn and winter, and two solar terms in each month. Each solar term has its own unique meaning. It is not only a seasonal system that guides agricultural production, but also a folk system that contains rich folk customs.

"Twenty-four solar terms" is the product of ancient farming civilization. It is a knowledge system formed by ancient ancestors following the farming season and observing the movement of celestial bodies to understand the changing laws of seasons, climate and phenology in a year.

After historical development, the lunar calendar absorbed solar terms of the dry calendar as a supplement to the calendar, and adjusted it to conform to the tropic year through the leap method, forming a combined calendar of yin and yang, and the "24 solar terms" became an important part of the lunar calendar. In the field of international meteorology, the 24 solar terms are known as "the fifth invention of China".