Sunset Autumn Equinox 2025 Calendar. It is also called the autumnal equinox, fall equinox or the beginning of autumn. The equinox and solstice define the transitions between the seasons of the astronomical calendar and are a key part of the earth's orbit around the sun.

Autumn / fall equinox 2024. The first day of autumn often called fall (september equinox or autumnal equinox) is when the sun shines directly on the celestial equator passing from north to south and the length of day and night are almost the same.