What does Diary 59 mean?

This is a folk solar term. See Dunhuang document Bo 40 17 "Poems on Ninety-nine" for the earliest number of nine poems handed down from generation to generation: May 9th, the white ones are getting longer and longer, and the sun can shine into the room after it comes out. The first day after May 9th is the 29th of the twelfth lunar month and New Year's Eve. As far as most parts of China are concerned, the weather was not the coldest when the 29th passed, but "1929, I can't reach it." At the end of April 9, it was almost the "Great Cold" solar term, so we said "3949". After May 9, the earth gradually rejuvenated and the weather gradually warmed from cold, so "May 969, look at the willows by the river; 7989, walking alone. " By 1999, it was already a "thunder" solar term, so the thunder of 1999 made a lasting noise.