Autumn Equinox 2025 Date. When do the four seasons start in 2025—for spring, summer, fall, and winter? In 2025, the autumnal (fall) equinox arrives on sunday, september 22, marking the official first day of fall.


Autumn Equinox 2025 Date

At an equinox, the sun appears directly above earth’s equator. An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length.

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