The western-edge effect
Chicago sits at the far western edge of the Eastern time zone, so its solar noon comes late — around 12:50 CST in winter and 13:30 CDT in summer. That makes Chicago's summer sunsets spectacularly late for its latitude: past 20:25 CDT in late June, with the winter solstice still delivering 9 hours 20 minutes of daylight.
Lake Michigan light
On the lakefront, the horizon is genuine water — the calculator's sunrise times are almost exactly what you see from North Avenue Beach. In winter, the sun rises over the lake to the southeast, and 'sunrise over frozen Lake Michigan' is one of the city's best photographic constants.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- NOAA Global Monitoring Laboratory — Solar Calculator — the solar position algorithm underlying sunrise, sunset and solar noon.
- NASA Science — Sun — solar geometry and the definition of civil, nautical and astronomical twilight.
- NIST Time and Frequency Division — time standards and the definition of the day.
Figures, formulas and reference tables last verified: 24 September 2026.