The Origin of the Zulu Time Zone

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"Zulu Time" is another term for General Mean Time or more recently Coordinated Universal Time (UTC) used by The National Oceanographic and Atmospheric Administration (NOAA) and The National Weather Service (NWS).  UTC is the French initials for Coordinated Universal Time - french still considered the official language of the United Nations. The origin of the term ZULU Time and what it represents evolved over centuries with the quest to measure time and the longitude.


The fervent desire to determine the longitude at a given  location was prompted by a fatal shipwreck. On October 22, 1707, four British Men 'O War sank just off the Cornish Coast. 2000 men were lost. In 1714, The British Parliament , aggravated by this obviously needless catastrophe, passed the Longitude Act: A huge sum of money would be awarded to anyone who could invent a way to determine the precise longitude of a ship's location to within less than one degree. After many years of tireless work it was John Harrison a great self taught British clockmaker who after many prototypes crafted a seaworthy chronometer.  (term not to be confused with the Chronometer awarded as precision watches by the C.O.S.C) As a result of a dispute his accomplishments were not acknowledged until George III intervened on his behalf.  John Harrison received his prize at the age of 81 - he died three years later.

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Time and longitude are intrinsically interwoven as to know ones Longitude at sea, one must know the time at home port and simultaneously know the time on ship. Once the time difference is known, the difference by degrees is known and thus the crucial longitude. The world spins on it axis 360 degrees in a 24 hour period thus in one hour it turns 15 degrees. If the navigator resets his ship's clock local at high noon, and refers to his clock representing time at the home port, every hour difference translates to 15 degrees from the home port.  Thus for  navigation of the oceans it was crucial to have an efficient chronometer on board.

In those seafaring days, global  admiration was bestowed upon the British Royal Navy for their superior seamanship and celestial navigation.  This made American Sea Captain Nathanial Bowditch quite peeved.  It was at the end of the American Revolutionary War and Nathanial Bowditch wanted to prove that the American Sea Captains were as good ,if not better, than their British rivals, so he set about proving this, not by canons or pistols, but by the power of the written word.
He wrote the iconic navigation textbook, "The American Practical Navigator" published in 1802.  This book took the seafaring community by storm - it was announced: "This Navigation textbook in sea-surface celestial navigation is the best book ever written on this subject !"
This book is still used today by The U.S Naval Academy, The U.S. Coastguard and the U.S. Merchant Marine Academy.  In his book he emphasized the need for knowing the local time in the log books of ships.

This was prior to Sandford Flemming's 1876 idea of a  24 hour clock or a Universal time zone.  You see Sandford Flemming had not missed his train at a lonely railway station in Ireland yet.  His printed schedule had not printed pm instead of am yet (prompting him to create the 24 hour clock and a Standardized Universal Time Zone).  In fact Sandford Flemming had not even been born yet.  So local time was still critical for ship logs.
In his textbook, Bowditch designated the prime meridian (0°longitude) as the center of a 15 ° time zone with 7.5 °on either side.  He performed this calculation with all the remaining 23 longitudes - each the center of a time zone straddled on either side by 7.5°.  Bowditch then labeled each of the time zones ,he created, with a letter from the alphabet. He commenced with the 1st time zone ,East of the Prime Meridian centered around 15° longitude, labeling it as time zone A.  He then worked his way East labeling the next time zone "B" then "C" and so on. However as expected at the International Date Line he ran into a slight problem, for although the time was technically the same on either side of the 180°, they were in actual fact different days! To avoid confusion he used only a 7.5° time zone East of the International Date line from 172.5° to 180° labeling it as  "M".  Rather than hopping over the International Date Line and commencing with his Eastward labeling journey, he began again at the 15° West of the prime meridian labeling that time zone "N".  Then journeying to the International Date Line from the West, he labeled the final 7.5° "Y".  That left the letter "Z" for the Prime Meridian Time Zone passing through Royal Observatory, Greenwich in southeast London, England.  The Z-time zone created in this way by Bowditch stuck and the Z time is listed on almost all navigational, astronomical and meteorological charts today.
Interestingly we know there are 26 letters in the English Alphabet and 25 time zones on Bowditch's chart, so which letter was omitted.  That letter was "J", since it was not a common letter in most languages.

So how did Z-time zone become ZULU TIME. Ever heard a pilot spelling out a name, a destination or missions over the roar of an engine using whole words starting with the letter required for the spelling of a single word.  "This mission is BRAVO, ALFA, TANGO (BAT)".  This is the NATO phonetic alphabet or ICAO phonetic used by pilots, soldiers, captains or anyone who needs to transmit critical auditory messages by radio or telephone.  The alphabet was specially designed to increase clarity, reduce confusion, avoid misunderstanding.  This alphabet was used in civil aviation in World War II.

This ZULU time refers to z-time which refers to the Greenwich Mean Time or "UTC", "GMT".  "GCT" or "Z"

Reference:
Z-Time written by Harold F. Maybeck, Plymouth State College
Wikipedia: Sanford Fleming
Wikipedia: NATO phonetic Alphabet
Longitude by Dava Sobel