Coordinated Universal Time follows a similar format, but the start time of each day depends on a person's location on the globe. UTC, typically referred to as Greenwich Mean Time, or ZULU time, has as its origin Greenwich, England. When it is midnight in Greenwich, we consider that to be the beginning of a new day worldwide. Why one time standard? Imagine communicating with an amateur radio operator on the other side of the Earth. Most hams maintain a log book which includes information about frequency used, time, and remarks. Matters are greatly simplified when all operators include a time entry which is the same worldwide. Rather than noting local time, entries are typically written as UTC. For similar reasons, NASA maintains all of its times in UTC, and all satellite tracking software requires the knowledge and use of UTC.