How did Sanjiutian come from?

20 18-0 1-09 is the first day of Sanjiu.

China has been in cold weather for several years since the winter of November. Astronomical experts say that the Ninth Five-Year Plan is a more applicable solar term in northern China, especially in the middle and lower reaches of the Yellow River. From the day of winter solstice, it entered the "number nine", commonly known as "cross nine", and then every nine days as a unit, called "nine". After nine "nines", it is exactly eighty-one days, that is, "nine out", and then spring blossoms.

"1929 don't make a move,

Walking on the ice in 3949,

59 and 69, looking at the willows by the river,

The river froze in' 79, and swallows flew in' 89.

99 plus 19, plowing cattle everywhere. "