Overview

• NASA places the 2025 autumnal equinox at 2:19 p.m. Eastern, a single instant experienced worldwide (7:19 p.m. in the UK).
• Day and night are only nearly equal today because daylight is measured by the Sun’s upper limb and bent by the atmosphere, with true local equality (the equilux) arriving days later in many places.
• Meteorologists define fall by temperature cycles starting Sept. 1, differing from the astronomical season that begins at the equinox.
• From today, daylight steadily wanes toward the winter solstice on Dec. 21, with clocks changing on Oct. 26 in the UK and Nov. 2 in the U.S.
• Aurora prospects typically improve around the equinoxes, when geomagnetic activity tends to be stronger.