Why is winter solstice and Qingming solar calendar, while Dragon Boat Festival and Mid-Autumn Festival are different every year?

Solstice and Qingming in winter belong to the twenty-four solar terms. The 24 solar terms are relatively fixed.

The twenty-four solar terms are named according to the position of the earth in the orbit of revolution and the weather and natural landscape at that time.

The collocation of 24 solar terms and Lunar Moon is not fixed and consistent every year.

Because the lunar calendar is based on the first month of the lunar calendar, the lunar month cannot accurately represent the specific time in the 24 solar terms, while the solar calendar is based on the tropic year and can accurately reflect the specific time in the 24 solar terms.

Dragon Boat Festival and Mid-Autumn Festival are two festivals in the lunar calendar, which are made according to the time of the lunar calendar.