When Is The Vernal Equinox 2024 In India. The modern iranian calendar year begins with the vernal equinox, as determined by observation in tehran. The vernal equinox — is an astronomical phenomenon when the sun, in its visible motion along the ecliptic, crosses the celestial equator.

This day is also considered the astronomical beginning of the spring season. The vernal equinox, occurring on march 19 to 21, signals the moment when the earth’s axis aligns with its orbit around the sun,.