Is there any relevant basis in Buddhism that you can't get a haircut in the first month? What should we do?

It should be a folk custom not to get a haircut in the first month. Cut your hair as follows.

Manjusri Bodhisattva shaved her head and lived a good life.

Blessed on the first day, happy on the third day.

The fourth day is rich ★ The fifth day is bloody, and the sixth day is magical ★

The seventh day of Kangning ★ the eighth day of longevity ★ the ninth day of smell ★

On the tenth day, we can determine eleven points and twelve hardships.

Thirteen small white and fourteen gods decide the 15th Universiade.

Sixteen benefits √ seventeen diseases and eighteen diseases.

Nineteen Enlightenment √ Twenty evils worship twenty-one adversity.

Twenty-two recipients smell twenty-four fruits.

Twenty-five fights for twenty-six auspicious ends √ twenty-seven sores and tinea.

Twenty-eight victims, twenty-nine long wisdom √ thirty good wishes √.

(the date is the Buddhist calendar, that is, the lunar calendar)