The military time zones are a standardized, uniform set of

time zone A time zone is an area which observes a uniform standard time for legal, Commerce, commercial and social purposes. Time zones tend to follow the boundaries between Country, countries and their Administrative division, subdivisions instead of ...

s for expressing time across different regions of the world, named after the

NATO phonetic alphabet The (International) Radiotelephony Spelling Alphabet, commonly known as the NATO phonetic alphabet, is the most widely used set of clear code words for communicating the letters of the Roman alphabet, technically a ''radiotelephonic spellin ...

. The Zulu time zone (Z) is equivalent to

Coordinated Universal Time Coordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about one second of mean solar time (such as UT1) at 0° longitude (at the IERS Reference Meridian as the currently used ...

(UTC) and is often referred to as ''the'' military time zone. The military time zone system ensures clear communication in a concise manner, and avoids confusion when coordinating across time zones. The

CCEB The Combined Communications-Electronics Board (CCEB) is a five-nation joint military communications-electronics (C-E) organisation whose mission is the coordination of any military C-E matter that is referred to it by a member nation. The member nat ...

, representing the

armed forces A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...

of Australia, Canada, New Zealand, the United Kingdom, and the United States, publishes the military time zone system as the ACP 121 standard. The armed forces of Austria and many nations in

NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...

use it.

Description

Going east from the

prime meridian A prime meridian is an arbitrary meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great c ...

at Greenwich, letters "Alfa" to "Mike" (skipping "J", see below) represent the 12 time zones with positive UTC offsets until reaching the

international Date Line The International Date Line (IDL) is an internationally accepted demarcation on the surface of Earth, running between the South and North Poles and serving as the boundary between one calendar day and the next. It passes through the Pacific O ...

. Going west from Greenwich, letters "November" to "Yankee" represent zones with negative offsets. The letters are typically used in conjunction with military time. For example, 6:00 a.m. in zone UTC−5 is written "0600R" and spoken "zero six hundred Romeo". The numeric zone description or "plus and minus system" indicates the correction which must be applied to the time as expressed in order to convert to UTC. For example, the zone description for the Romeo time zone is +5. Therefore, adding 5 hours to 0600R produces the time in UTC, 1100Z. The letter "J" ("Juliet"), originally skipped, may be used to indicate the observer's local time. The letter 'L' was previously misidentified in some editions of U.S. Army publications, such as FM 5-0, as representing 'Local' time, which conflicted with its established use for the Lima time zone (UTC+11). This error has been rectified in the latest edition of FM 5-0, released in May 2022, which no longer includes this incorrect usage. "LT" may also (rarely) be used to denote local time. The letter "N" is also used to designate zone −13; this is to provide for a ship in zone −12 keeping Daylight Saving Time. The letter "Z" ("Zulu") indicates

(UTC). The ACP 121 standard actually refers to

Greenwich Mean Time Greenwich Mean Time (GMT) is the Local mean time, mean solar time at the Royal Observatory, Greenwich, Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, i ...

(GMT) as the base time standard, but UTC has superseded GMT as a more precise time standard, so the time offsets are commonly understood as UTC.

History

Sandford Fleming devised a system assigning the letters A–Y excluding J to 1-hour time zones, which may have been the inspiration for the system. The standard was first distributed by

as a note in 1950. The note states "This method is based on the systems in use in the Armed Forces of these countries and the United States". The British used a system of lettered zones, which was likely the direct influence. RFC 733 published in 1977 allowed using military time zones in the field of

email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant ...

s. RFC 1233 in 1989 noted that the signs of the offsets were specified as opposite the common convention (e.g. A=UTC−1 instead of A=UTC+1), and the use of military time zones in emails was deprecated in RFC 2822 in 2001. It is recommended to ignore such designations and treat all such time designations as UTC unless out-of-band information is present.

Description

History

See also

Notes

References

External links