Why do children have to cut their hair on the first or fifteenth day?

It's easy to remember the time interval. /kloc-once every 0/5 days, the hair won't be too long. Very healthy! Um ... . . The above is pure nonsense. According to folk sayings, the fifteenth day of the first lunar month is an auspicious day, and all evil spirits will not invade. However, in ancient China, it was always believed that hair was made up of human qi and blood, which cut off its vitality and was easily invaded by evil spirits. Therefore, it was chosen on the fifteenth day of the first lunar month to protect itself from evil spirits.