Below is a list of Williamstown OH zip codes. For your research we have also included Williamstown Area Code, Time Zone, UTC and the local Hancock County FIPS Code. Each Williamstown Ohio zip code has a center Longitude / Latitude point (the Williamstown center is -83.651397705078 / 40.83390045166). For your convenience we have also indicated if that zip code in Williamstown observes Daylight Savings time.