Y-Day - All About All

Military designation of days and hours (Redirected from Y-Day)

The military designation of days and hours within the North Atlantic Treaty Organisation (NATO), is specified in AAP-6 (STANAG 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 (http://www.dtic.mil/doctrine/jel/new_pubs/jp1_02.pdf).

• B-Day is used informally as short-hand for "birthday".
• C-Day is the unnamed day on which deployment for an operation commences. (US)
• D-Day is 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 is D-Day, June 6, 1944, when "Operation Overlord" began. (NATO)
• E-Day is the unnamed day on which a NATO exercise commences. (NATO)
• F-Hour is the effective time of announcement by the U.S. Secretary of Defense to the Military Departments of a decision to mobilize Reserve units. (US)
• G-Day is the unnamed day on which an order, normally national, is given to deploy a unit. (NATO)
• H-Hour is 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)
• I-Day is used informally within the U.S. military bureaucracy to variously designate the "Implementation Day" or the (Delivery Order) "Issuance Day".
• ­J-Day was used during both world wars [1] (http://www-cgsc.army.mil/carl/resources/csi/iib_iji/iib_iji.asp) to designate the day an assault (sometimes amphibious [2] (http://www.uscg.mil/hq/g-cp/history/Saipan.html)) occured.
• K-Day is the unnamed day on which a convoy system is introduced or is due to be introduced on any particular convoy lane. (NATO)
• L-Hour is the specific time at which deployment for an operation commences. (US)
• M-Day is the unnamed day on which mobilization commences or is due to commence. (NATO)
• N-Day is the unnamed day an active duty unit is notified for deployment or redeployment. (US)
• O-Day is a Maritime Prepositioning Force (MPF, the vanguard of a Marine Air-Ground Task Force, MAGTF) term designating the day the Maritime Prepositioning Ship Squadron (MPSRON) off-load begins, or the continuous flow of the Fly-In Echelon (FIE) commences, whichever is later. [3] (http://www.jdtc.jfcom.mil/DeploymentGlossary/terms%20e-h.htm)[4] (http://www.jdtc.jfcom.mil/DeploymentGlossary/terms%20m-p.htm)
• P-Day is 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)
• Q-Day was 23 June 1945, the day of the dress rehearsal of the first atom bomb test [5] (http://www.history.navy.mil/books/OPNAV20-P1000/Q.htm); nowadays it is sometimes used informally to mean "Quality Day", or the first day of the calendar quarter.
• R-Day is the unnamed day on which redeployment of major combat, combat support, and combat service support forces begins in an operation. (US)
• S-Day is the unnamed day the President authorizes Selective Reserve callup (not more than 200,000 men). (US)
• T-Day is 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)
• V-Day is sometimes used to designate "Victory Day", the day an operation successfully concludes; it is also used informally as short-hand for "Valentine's day".
• V-E Day ("Victory in Europe") designates 8 May 1945, the date when the Allies formally celebrated the defeat of Nazi Germany.
• V-­J Day ("Victory over Japan") designates 14 August 1945, the date of Japan's acceptance of the unconditional surrender terms.
• W-Day is the effective day the President takes the adversary decision to prepare for war (unambiguous strategic warning). (US)
• X-Day was 1 November 1945, the day Operation Olympic (the invasion of Japan) was to begin [6] (http://www-cgsc.army.mil/carl/resources/csi/huber2/huber2.asp). The term also generically means "attack day".
• Y-Day was 1 March 1946, the day Operation Coronet (the invasion of Tokyo Plains) was to occur. [7] (http://www-cgsc.army.mil/carl/resources/csi/huber2/huber2.asp)
• Z-Day was 10 June 1945, the day the Australian Imperial Forces landed in Brunei Bay to liberate Brunei, part of Operation Oboe Six. [8] (http://www.history.navy.mil/danfs/t6/titania.htm) [9] (http://www.bruneidarussalam.embassy.gov.au/media/oboe_six.html)