Is Tomb-Sweeping Day based on the solar or lunar calendar?

According to the lunar calendar, to be exact, it is calculated according to the ecliptic, but it usually falls on April 4 or April 5 of the solar calendar.

The weather in Tomb-Sweeping Day is usually around April 5th of the Gregorian calendar, that is, the first15th day after the vernal equinox. Tomb-Sweeping Day period is very long, 8 days before 10 and 10 days before 10. These nearly 20 days belong to the Tomb-Sweeping Day period. Tomb-Sweeping Day, Dragon Boat Festival, Spring Festival and Mid-Autumn Festival are also called the four traditional festivals in China.

Tomb-Sweeping Day is a traditional festival in China. Many vagrants come home from outside to sweep graves to worship their ancestors. And the reason why they will come to the grave in early spring is that everything will start to grow after being frightened, and the rain in spring will easily collapse the grave, so they should come to the grave in early spring.