First Day Of Spring 20243. The first day of spring (march equinox or vernal equinox) is when the sun shines directly on the celestial equator passing from south to north and the length of day and night are almost the same. Traditionally, the first day of spring is marked by the spring equinox, which falls in march every year.

Leap years are caused by earth’s rotation. The march or vernal equinox is when the sun crosses the celestial equator, moving from south to north.