What is "Zulu" time?
Zulu (short for "Zulu time") is used in the military and in navigation generally as a term for Universal Coordinated Time (UCT), sometimes called Universal Time Coordinated ( UTC ) or Coordinated Universal Time (but abbreviated UTC), and formerly called Greenwich Mean Time. In military shorthand, the letter Z follows a time expressed in Greenwich Time. Greenwich Time, now called Universal Coordinated Time, is the time at longitude 0 degrees 0 minutes - the prime meridian or longitudinal line that separates East from West in the world geographical coordinate system. This line of longitude is based on the location of the British Naval Observatory in Greenwich, England, near London. "Zulu" is the radio transmission articulation for the letter Z.
.Traditionally, ship and airplane navigation is conducted using Zulu time. Zulu time is usually expressed in terms of a 24-hour clock using the Gregorian calendar time divisions of hours and minutes.
"Zulu" time is that which is more commonly know as "GMT" (Greenwich Mean Time). Our natural concept of time is linked to the rotation of the earth and we define the length of the day as the 24 hours it takes (on average) the earth to spin once on its axis.
As time pieces became more accurate and communication became global, there needed to be a point from which all other world times were based. Since Great Britain was the world's foremost maritime power when the concept of latitude and longitude came to be, the starting point for designating longitude was the "prime meridian" which is zero degrees and runs through the Royal Greenwich Observatory, in Greenwich, England.
When the concept of time zones was introduced, the "starting" point for calculating the different time zones was agreed to be the Royal Greenwich Observatory.
Unfortunately the Earth does not rotate at exactly a constant rate. Due to various scientific reasons and increased accuracy in measuring the earth's rotation, a new timescale, called Coordinated Universal Time (UTC), has been adopted and replaces the term GMT.
The Navy, as well as civil aviation, uses the letter "Z" (phonetically "Zulu") to refer to the time at the prime meridian.
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