What is three or nine days?

Three or nine days refers to the third "nine days" from winter to Sunday, that is, 19-27 days from winter to the future. China lunar calendar uses "99" to calculate seasons. The first day of the winter solstice is "19 days", and every 9 days is a "9". The first nine days are called "19", the last nine days are called "29" and so on. "99" 81days later, winter ends and spring enters, and the coldest period of the year is.

When the sunshine time from winter solstice is the shortest, the heat absorbed is the least, but at this time, the heat on the ground is still in reserve and the ground temperature has not reached the lowest point, so the winter solstice is not the coldest time.

However, due to the winter solstice, the heat consumed by the ground is far greater than the heat absorbed, and the ground heat will gradually make ends meet and consume more and more heat. It's basically the lowest ground temperature in three or nine days. After 39 days, the sun exposure time will gradually increase, and the ground temperature will gradually increase. This is why it was cold on March 9th.

Extended data

3. The cold weather in September is the season with high incidence of joint degeneration, neck, shoulder, lumbocrural pain, allergic rhinitis, facial paralysis, asthma, gastrointestinal diseases and sub-health.

The so-called "cold is hot" can be moxibustion for three or nine days, and Chinese medicine can be applied to acupuncture points with specific curative effects to achieve the purpose of getting rid of diseases. It has obvious therapeutic effect on some diseases of deficiency-cold and some of them can achieve radical effect. This is an effective thermotherapy.

Baidu Encyclopedia-Sanjiutian