Cleveland Abbe
In order to compile his information, Abbe required a time-keeping system that was consistent among the stations. To accomplish this he divided the United States into four standard time zones. He published, in 1879, a paper titled "Report on Standard Time". In 1883, he convinced North American railroad companies to adopt his time-zone system. In 1884, Britain, which had already adopted its own standard time system for England, Scotland, and Wales, helped gather international consent for global time. In time, the American government, influenced in part by his 1879 paper, adopted the time-zone system.
Coordinated Universal Time
The time zone using UTC is sometimes denoted or by the letter "Z"—a reference to the equivalent nautical time zone (GMT), which has been denoted by a "Z" since about 1950. Time zones were identified by successive letters of the alphabet and the Greenwich time zone was marked by a "Z" as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see time zone history). Since the NATO phonetic alphabet word for "Z" is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard. This ensures that all pilots, regardless of location, are using the same 24-hour clock, thus avoiding confusion when flying between time zones. See the list of military time zones for letters used in addition to "Z" in qualifying time zones other than Greenwich.