The military designation of days and hours within the

North Atlantic Treaty Organization 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 ...

(NATO), is specified in AAP-6 (

STANAG In NATO, a standardization agreement (STANAG, redundantly: STANAG agreement) defines processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance. Each NATO st ...

3680), ''NATO Glossary of Terms and Definitions'', and marked ''(NATO)'' in what follows. Those entries marked ''(US)'' are specific to the U.S., and defined only in Joint Publication JP 1-02
''Department of Defense Dictionary of Military and Associated Terms''
References to days (or hours) preceding or following a designated day (or hour) use a plus or minus sign and an Arabic numeral following the letter. For example, "D−3" is 3 days prior to D-Day, "C+7" is 7 days after C-Day, "H−2" is 2 hours before H-hour, and so forth. In less formal contexts, the time is usually spelled out, so that "D−3" becomes "D minus three" or "D minus 3". ; :20 October 1944, the day the

Leyte Island Operation Leyte ( ) is an island in the Visayas group of islands in the Philippines. It is eighth-largest and sixth-most populous island in the Philippines, with a total population of 2,626,970 as of 2020 census. Since the accessibility of land has be ...

(the

invasion of Leyte An invasion is a military offensive in which large numbers of combatants of one geopolitical entity aggressively enter territory owned by another such entity, generally with the objective of either: conquering; liberating or re-establishing con ...

) began. ; :Short for "Commencement Day" which usually means when

deployment Deployment may refer to: Engineering and software Concepts * Blue-green deployment, a method of installing changes to a web, app, or database server by swapping alternating production and staging servers * Continuous deployment, a software en ...

for an

operation Operation or Operations may refer to: Arts, entertainment and media * ''Operation'' (game), a battery-operated board game that challenges dexterity * Operation (music), a term used in musical set theory * ''Operations'' (magazine), Multi-Ma ...

commences. It is called "Commencement Day" because before deployment candy is usually passed out to G.I.s from charitable organizations. ''(US)'' ; (

redundant acronym RAS syndrome (where "RAS" stands for "redundant acronym syndrome", making the phrase "RAS syndrome" homological) is the redundant use of one or more of the words that make up an acronym (or other initialism) in conjunction with the abbreviated f ...

of day since the D stands for day, so it means day-day) :The unnamed day on which an operation commences or is due to commence. This may be the commencement of hostilities or any other operation. The most famous

D-Day The Normandy landings were the landing operations and associated airborne operations on Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as D ...

was June 6, 1944, when "

Operation Overlord Operation Overlord was the codename for the Battle of Normandy, the Allies of World War II, Allied operation that launched the successful invasion of German-occupied Western Front (World War II), Western Europe during World War II. The operat ...

" began. Contrary to popular belief, the "D" does not stand for any specific word – the most popular being disembark. ''(NATO)''. According t

the "D" stands for "Day". ; :The unnamed day on which a NATO exercise commences. ''(NATO)'' ; :The effective time of announcement by the U.S. Secretary of Defense to the Military Departments of a decision to mobilize Reserve units. ''(US)'' ; :The unnamed day on which an order, normally national, is given to deploy a unit. ''(NATO)'' ; (

hour An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earth's rotation. There are 60 minutes in an hour, and 24 ho ...

since the H stands for hour so it means hour-hour) :The specific time at which an operation or exercise commences, or is due to commence (this term is used also as a reference for the designation of days/hours before or after the event). ''(NATO)''; also known as Zero Hour ; :Used informally within the U.S. military bureaucracy to variously designate the "Implementation Day" or the (Delivery Order) "Issuance Day". ; :Used during both world wars to designate the day an assault occurred. ; :The unnamed day on which a

convoy A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support and can help maintain cohesion within a unit. It may also be used ...

system is introduced or is due to be introduced on any particular convoy lane. ''(NATO)'' ; :The specific time at which deployment for an operation commences. ''(US)'' ; :For "Landing Day", 1 April 1945, the day

Operation Iceberg Operation or Operations may refer to: Arts, entertainment and media * ''Operation'' (game), a battery-operated board game that challenges dexterity * Operation (music), a term used in musical set theory * ''Operations'' (magazine), Multi-Man ...

(the

invasion of Okinawa The , codenamed Operation Iceberg, was a major battle of the Pacific War fought on the island of Okinawa by United States Army (USA) and United States Marine Corps (USMC) forces against the Imperial Japanese Army (IJA). The initial invasion of ...

) began. ; :The day on which

mobilization Mobilization is the act of assembling and readying military troops and supplies for war. The word ''mobilization'' was first used in a military context in the 1850s to describe the preparation of the Prussian Army. Mobilization theories and ...

commences or is due to commence. ''(NATO)'' ; :The unnamed day an active duty unit is notified for deployment or redeployment. ''(US)'' ; :A

Maritime Prepositioning Force Strategic sealift ships are part of the United States Military Sealift Command's (MSC) prepositioning program. There are currently 17 ships in the program, strategically positioned around the world to support the Army, Navy, Air Force, Marine Corp ...

(MPF, the vanguard of a

Marine Air-Ground Task Force Marine Air-Ground Task Force (MAGTF, pronounced MAG-TAF) is a term used by the United States Marine Corps to describe the principal organization for all missions across the range of military operations. MAGTFs are a balanced air-ground, combined ar ...

, MAGTF) term designating the day the Maritime Propositioning Ship Squadron (MPSRON) off-load begins, or the continuous flow of the Fly-In Echelon (FIE) commences, whichever is later. ; :The expected date at which the rate of production of a consumable equals the rate at which the item is required by the Armed Forces. ''(US)'' ; :23 June 1945, the day of the dress rehearsal of the first atom bomb test nowadays it is sometimes used informally to mean "Quality Day", or the first day of the calendar quarter. ; :The unnamed day on which redeployment of major combat, combat support, and combat service support forces begins in an operation. ''(US)'' ; :The unnamed day the President authorizes Selective Reserve callup (not more than 200,000 men). ''(US)'' ; :The effective day coincident with Presidential declaration of national emergency and authorization of partial mobilization (not more than 1,000,000 personnel exclusive of the 200,000 callup). ''(US)'' ; :Sometimes used to designate "Victory Day", the day an operation successfully concludes. ; :"Victory in Europe"; designates 8 May 1945, the date when the Allies formally celebrated the defeat of

Nazi Germany Nazi Germany (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...

. ; :"Victory over Japan"; designates 14 August 1945, the date of Japan's unconditional surrender. ; :The effective day the President takes the adversary decision to prepare for war (unambiguous strategic warning). ''(US)'' ; :1 November 1945, the day

Operation Downfall Operation Downfall was the proposed Allied plan for the invasion of the Japanese home islands near the end of World War II. The planned operation was canceled when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki, th ...

(the invasion of Japan) was to begin. The term also generically means "attack day". ; :1 March 1946, the day Operation Coronet (the invasion of Tokyo Plains) was to occur. ; :10 June 1945, the day the Australian Imperial Forces landed in

Brunei Bay Brunei Bay ( ms, Teluk Brunei) is on the northwestern coast of Borneo island, in Brunei and Malaysia. Brunei Bay is located 5°00'43.44", 115°17'26.66"; east of Bandar Seri Begawan, Brunei. It is the ocean gateway to the isolated Temburong Dis ...

to liberate

Brunei Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi alphabet, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely sur ...

, part of

Operation Oboe Six The Battle of North Borneo took place during the Second World War between Allied and Japanese forces. Part of the wider Borneo campaign of the Pacific War, it was fought between 10 June and 15 August 1945 in North Borneo (later known as Sabah) ...

References

{{reflist Military terminology