Vernal Equinox 2025. The vernal equinox — is an astronomical phenomenon when the sun, in its visible motion along the ecliptic, crosses the celestial equator. This date marks the spring equinox in the northern hemisphere.
Also called the vernal equinox, this is the time of year when (due to the earth’s tilt and orbit) the sun appears to move above the celestial equator in the sky. In 2025, the official first day of spring is thursday, march 20.