September 27, 2026: Daylight falls below 12 hours across the northern hemisphere. Learn why daylight and nighttime are not equal at the equinox and how the changing season affects skywatching.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:44 a.m. CDT; Sunset, 6:39 p.m. CDT. Times are calculated by the US Naval Observatory’s MICA computer program. Check local sources for sunrise and sunset times.
Venus as an Evening Star
Daylight Shortens
Daylight’s length slips below 12 hours across the northern hemisphere. Because of the manner in which sunrise and sunset are calculated, using the top edge of the sun rather than the center and accounting for atmospheric refraction near the horizon, daylight and nighttime are not equal at the equinox. Theoretically, they are equal, although under today’s conventions they are not.
City Comparisons
In Chicago, daylight spans 11 hours, 55 minutes, while in Miami it is six minutes longer. At Miami’s latitude and southward toward the equator, the sun remains in the sky for over 12 hours. In Anchorage, daylight lasts 11 hours, 46 minutes. At more southerly latitudes, such as Auckland, daylight spans 12 hours, 17 minutes. In comparison, Nashville receives 11 hours, 58 minutes of sunshine. Auckland and Nashville are nearly equidistant from the equator.
Daylight decreases fastest at the more northerly latitudes. While Anchorage experienced long spans of sunshine and no complete darkness earlier during the summer, it now has the shortest daylight interval among the cities regularly noted in these articles. It continues to lose daylight faster than the other locations.
Near the equator, Miami’s daylight interval drops below 12 hours tomorrow.
Autumn’s Changing Night Sky
As daylight shrinks across the northern hemisphere, nighttime celestial events occur earlier compared to sunset and later compared to sunrise. After sunset, Saturn nears opposition early next month, making it easier to see. Before sunrise, winter’s Orion stands in the southern sky during October’s morning twilight. The seasonal transition is evident both in the shortening daylight and in the changing appearance of the night sky.
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