12 Hour time clock and 24 hour military time
12 Hour time clock and 24 hour military time
A 24 hour clock is used by the Military as well as other agencies, businesses and people. It is a method of keeping time from midnight to midnight and is divided into 24 hours. It is commonly used throughout the world.
The time chart to the left shows how a 12 hour am / pm clock relates to 24 hour Military time. The time table also indicates how military time is spoken.
The military time also known as astronomical time starts at midnight which would be 0000 or may be referred to as zero hundred hours, the military does not call midnight twenty four hundred hours although it may be referred by that by others for midnight. Military personnel may make reference to a time such as 0500 in the words "zero five hundred hours or oh five hundred hours" which would be 5 am in the morning. Another example would be if a military officer was speaking with another he or she may speak of a meeting being set for "fourteen hundered hours" (1400 hrs) which would correspond to the time of 2 pm on a 12 hour time clock. A time of 7:30 pm on a 12 hour time would relate to the time of 1930 in military time. The last minute of the day in military time would be 2359 which is one minute before midnight. The colon is often left out of the time when it is written so 1452 would be the same as 14:52 which corresponds to 2:52 pm in civilian time.
Not only the military use military time, it is also used by private companies for recording shipments, payroll as well as day to day activities. Other organizations using military time , are public transportation, federal state and local governments, hospitals, emergency services as well as many computer systems. Greenwich Mean Time (GMT) is the Coordinated Universal Time zone that is often used and referred to as to avoid confusion with large scale operational matters such as ship movements, flights and communications within the military. It is designated with a Z at the end of the military time and known as Zulu time. An example would be 1642Z. Local time has a J (for Juliet) with it and is written as (1642J). This would be spoken as "sixteen forty two Juliet". The eastern time zone is indicated with an R for Romeo. So if the civilian times was 4:42 pm eastern time that would be 1642R in military time spoken as sixteen forty two Romeo. Each military time zone has a corresponding letter and name.
History
Around 2100 BC ancient Egyptians used 36 groups of small star constellations known as decans to tell time. Although modern astrologers mostly ingore decans they continued to be used throughout the Renaissance in astrology and magic.
The U.S. Navy adopted the 24 hour clock in 1920 but it took until 1942 for the U.S. Army to also adopt it.
For those interested in the history of mechanical clocks and watches check out watchranker.com.
References:
Wikipedia, Decans, December 30, 2018
Wikipedia, 24 Hour Clock June 5, 2014
About.com, US Military, June 24, 2014
WikiHow, How to tell Military Time, August 24, 2015
