The autumnal equinox signifies the sun's crossing of the celestial equator, initiating shorter days in the northern hemisphere.
Contrary to popular belief, the equinox doesn't mean perfectly equal day and night lengths due to atmospheric effects.
Atmospheric refraction causes light bending, adding a few extra minutes of daylight, making the day slightly longer than the night.
Consequently, the true equal day and night, or 'equilux,' arrives a few days after the equinox, around September 25th or 26th.
