Can't you get a haircut in the first month?

According to the concept of elders, you can't cut your hair in the first month, because it was considered unlucky in ancient times, so you should cut your hair before the Spring Festival, and you are not allowed to cut your hair again in the first month.

Although we are paying less and less attention to these taboos now, few shops are open in the first month, and it is not convenient to get a haircut. China people pay attention to do as the Romans do, so we should not underestimate our traditional customs too much.

The first month after the lunar calendar:

Later, the relevant month of the lunar calendar was called the first month of the lunar calendar, and the first month of the official calendar was silver moon, including beginning of spring and rainfall in the 24 solar terms. The lunar month in which the main time of 15 or 16 days after beginning of spring is located is determined. If you come late, you should add a lunar month as a leap month in the year before the lunar calendar, otherwise it will not match.

The first month of the solar calendar used in mathematics books: The so-called "building the yin in the first month" in ancient and modern mathematics literature does not refer to the lunar calendar, but refers to the lunar calendar that began on the first day of spring. In mathematics, the so-called "being robbed in Shanghai in the first month" refers to the solar calendar. If you don't understand the first two months, you won't understand the mathematician's book.