Play a place name in leap February

The answer to the February leap mystery is Changchun.

Leap February means that the lunar calendar has two February in a year, and the second February is leap February. Leaping into February is to prevent the lunar calendar from being out of touch with the tropic year, that is, the four seasons, because the next month after February of the lunar calendar has only solar terms, and Grain Rain after Qingming is postponed to next month, so there will be a month without neutral atmosphere after February. So the month without neutral atmosphere after February is named "leap February" after February, which is the reason for leap February.