Which of the 24 solar terms is the smallest?

There is no minimum time limit for solar terms. Solar terms refer to the 24 solar terms and climate, which is a supplementary calendar made by China to guide farming in ancient times. Because the traditional lunar calendar in East Asia is a kind of "yin and yang calendar", which is based on the movement of the sun and the moon, it can't fully reflect the solar cycle. But China is an agricultural society, and agriculture needs a strict understanding of the movement of the sun, so farming is entirely based on the sun. Therefore, the "twenty-four solar terms" that reflect the solar cycle alone are added to the calendar as the standard for determining leap months. In other words, the 24 solar terms are purely solar calendars, and they are not formulated according to the lunar calendar at all.