First Day Of Spring Day 2024. In the northern hemisphere, the astronomical start of spring is also known as the spring equinox. 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.
It marks almost equal lengths of day and night, although the amount of daylight is. In the northern hemisphere, the astronomical start of spring is also known as the spring equinox.