First Day Of Spring 2025 Usa Time. On the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator,. To calculate the first day of spring 2025, we need to determine the date of the vernal equinox, which is the day when day and night are equal in length.

It is also called the spring quinox. The first day of spring is in 2025 on march 20 (according to the astronomical definition).