What's the point of hanging green on a new grave?

The so-called "new grave doesn't match the society", in which the "society" refers to a solar term, that is, the fifth "E" day after the vernal equinox, and the countryside is also called the Spring Society, while the new grave refers to the grave that has been buried for less than three years. The whole sentence means that a new grave that has just been buried for less than three years must be "hung green" before or on the day of the Spring Festival, just like that family in the village.

Later, he asked the old man why the "hanging green" of the new grave could not exceed the "society". Can Qingming not go to the grave again? So the old man told me such an allusion, that is to say, people who have been dead for a long time have just arrived in another world, without friends, and are lonely and helpless. Sacrifices brought by Shi Yang's relatives may be taken away by other "people". In front of the clubhouse is the legal reception day of the underworld, at which time all the sacrifices brought to the new dead can be collected. The sacrifices brought to them during the Qingming period may not be collected, so they have to sweep the graves of those who have just passed away before the Spring Festival couplets and burn the sacrifices.

Having said that, everyone must understand what it means to "the new grave is not the club", but what does it mean to "the old grave is not the Qingming night"? In fact, this sentence is easy to understand, because after Qingming night, this solar term has passed, and it is meaningless to go to the grave again.

Solemnly declare: the answer is for reference only, please don't be blindly superstitious.