Vernal Equinox Day 2025. The spring equinox, also known as the vernal equinox, is one of the four solar festivals of the year. In other words, on the day of the vernal equinox, day.

The vernal equinox — is an astronomical phenomenon when the sun, in its visible motion along the ecliptic, crosses the celestial equator. In other words, on the day of the vernal equinox, day is almost equal to night, while the length of daylight continues to grow.