Below is a list of Dekalb County IL zip codes. For your research we have also included Dekalb County Area Code, Time Zone, UTC and the local County FIPS Code. Each Dekalb County Illinois zip code has a center Longitude / Latitude point (the Dekalb County center is -88.764801025391 / 41.910999298096). For your convenience we have also indicated if that zip code in Dekalb County observes Daylight Savings time.