Because the equinox dates shift slightly each year (due to the exact time it takes the Earth to orbit the sun), the months remain the same, but the dates change:
The start date varies slightly each year (by ±1 day) due to leap years and elliptical orbit mechanics. While the equinox is a precise moment in time, the surrounding days are considered "early spring." what month is in spring
In the Northern Hemisphere, spring typically occurs from . Spring in Japan: Your Seasonal Guide Because the equinox dates shift slightly each year