Below is a list of Mountainside NJ zip codes. For your research we have also included Mountainside Area Code, Time Zone, UTC and the local Union County FIPS Code. Each Mountainside New Jersey zip code has a center Longitude / Latitude point (the Mountainside center is -74.364501953125 / 40.676399230957). For your convenience we have also indicated if that zip code in Mountainside observes Daylight Savings time.