I pay attention to the sunrise/sunset times in both the Chicago Tribune and Daily Herald. Why are there discrepancies in the times?
The reason for the differences is the location used to determine the actual time of sunrise and sunset. In a large metropolitan area, the difference is noticeable. At Chicago’s latitude, the Earth rotates at a speed of about 13 miles a minute, so sunrise/sunset times vary by about a minute for every 13 miles of east-west travel, though north-south distances have little effect. The times at Crystal Lake, about 25 miles west of Chicago are about two minutes later. Chicago’s official times are determined by the U.S. Naval Observatory based on a reference point near the Stevenson Expressway and Western Avenue, a location representing the city’s population-weighted center.