At 405 am CDT Friday September 23rd, the autumnal equinox begins. This is when the Sun crosses the Equator on it's way to the southern hemisphere. While our fall starts, the austral spring begins. Although usually considered the date when the day is of equal length, at these mid latitudes that day is usually a day or so later. For the Grand Forks area, the date when sunrise and sunset are really almost equal is Sunday October 25th. Due to complexities of the Earths shape, its orbit, eccentricity and wobble, equal day and night vary.
For much more detailed information, visit the experts in everything Astronomical, the U.S. Navy Observatory.Their web services have a great deal of information, and are the official government source to look to for data.