Sunlight irradiation can promote blood circulation of human skin, accelerate skin metabolism and regulate human immune function. It can also kill many germs, and patients with psoriasis and rheumatoid arthritis will have a good adjuvant treatment effect if they spend more time in the sun. Sunlight can also promote the production of melanin in the skin and enhance the skin's resistance to ultraviolet rays. Most importantly, sunbathing can promote the skin to synthesize vitamin D3. Vitamin D3 can promote calcium absorption and bone formation. If vitamin D3 is insufficient, it will increase the possibility of rickets and other diseases. Besides, sunshine can make people feel happy. Sunlight exposure can change the content of some signal substances in the human brain, which makes people feel high and willing to engage in challenging activities. Spring, summer and autumn, 8 am to 10, and 4 pm to 7 pm are the best time to bask in the sun. At this time, the light should not be too strong. The sunlight is mainly a beneficial ultraviolet A beam, which can make the human body produce vitamin D, thus enhancing the anti-tuberculosis and osteoporosis prevention ability of the human immune system and reducing the incidence of arteriosclerosis. In winter, the sunshine at noon is the best. Winter is the season of dormancy and gestation, and it is also the most cloudy time of the year. At noon, it can be reconciled with the sun with strong yang. For the elderly, it is ok to bask in the sun for half an hour before or after a nap. But be careful, when sunbathing, you must take off your hat and let the sun shine directly on Baihui point above your head, so that Yang Can can enter your body.