The USA cuts into six time zones: Eastern, Central, Mountain, Pacific, Alaska, and the Hawaii-Aleutian. States observing DST add confusion with some states changing between standard time and daylight time. Besides the 50 states are U.S. territories Puerto Rico and Guam which account for three more time zones. It is essential information for traveling, communication, and business planning purposes. For meetings or flights, knowing U.S. time zones will save travelers from confusion and missed schedules.