Military designation of days and hours
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
. 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". A-Day was 20 October 1944, the day the Leyte Island Operation (the invasion of Leyte) began. B-Day has no military designation. C-Day is short for "Commencement Day" which usually means when deployment for an operation commences. It is called "Commencement Day" because before deployment candy is usually passed out to G.I.s from charitable organizations.