Solstice Equinox Dates 2025. The vernal equinox marks the. An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length.

An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length. An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length.