What does it mean to add soil to the grave in the Gregorian calendar on auspicious days?

Adding soil to the grave is an important part of Tomb-Sweeping Day's grave sweeping.

In the Ming Dynasty's "A Brief Introduction to the Scenery of the Imperial Capital", it was written: "On the Qingming Festival in March, men and women went to the grave to pay their respects, and the gold ingot was hung on the back of the sedan chair, and the road was full of embarrassment. Worshippers, mourners, weeping people, weeding people, and those who add soil to the grave will burn gold ingots every time and put paper money on the grave. "

Although "adding soil" is often symbolic, many of them are particular.

For example, the new grave cannot be filled for three years, which is said to be unfavorable to future generations.

For another example, when Tim Tu visited the grave in Tomb-Sweeping Day, he would check the Gregorian calendar at other times.