What's the significance of April leap?

Leap April means that there is no "neutral qi" in the lunar calendar, and it is called leap April after the lunar calendar. Since the Qin and Han Dynasties, the Chinese lunar calendar has been parallel to the twenty-four solar terms, guiding agricultural production with the twenty-four solar terms.

For example, 200 1 (Xinsi year of the snake), Xiaoman is May 2 1 (April 29th of the lunar calendar), and the first day of the next lunar month is May 23rd. However, this lunar month ends on June 20, and the summer solstice falls on June 2 1 day, so this lunar month is not "neutral", but in.