Which of the following is NOT included in United States Time Zones?

The choice of Greenwich is correct because it does not represent a time zone utilized within the United States. Instead, Greenwich Mean Time (GMT) represents the mean solar time at the Royal Observatory in Greenwich, London, and is used primarily as a reference point for coordinating time worldwide.

In contrast, Pacific, Central, and Mountain refer to specific time zones that are indeed part of the United States. The Pacific Time Zone covers states on the West Coast, the Central Time Zone corresponds to many states in the central part of the country, and the Mountain Time Zone is used in states that are primarily located in the Rocky Mountains region. Each of these time zones has its own standardized hours in relation to GMT or UTC, which is crucial for scheduling and synchronization across various regions in the U.S.