.  UTC is also sometimes called '''Z''' or '''Zulu''' time. A time may be written as e.g. 00:00Z with the Z indicating UTC. The "Z" is for "zero", and "Zulu" is the two-way radio pronunciation of "Z". It comes from the nautical system in which each time zone was assigned a letter.  UTC is also sometimes called '''Z''' or '''Zulu''' time. A time may be written as e.g. 00:00Z with the Z indicating UTC. The "Z" is for "zero", and "Zulu" is the two-way radio pronunciation of "Z". It comes from the nautical system in which each time zone was assigned a letter.  