When you first hear someone in the military give you the time, you may have to pause a few seconds and do the quick math in order to determine the time of day.
Unless you grew up in a military household, you are likely not familiar with how the military tells time.
Civilians typically break up the day into a.m. and p.m., which are two 12-hour blocks of the day denoting morning and afternoon or evening.
The 24-Hour Military Time Clock
The military operates off a 24-hour clock, beginning at midnight (which is 0000 hours). So, one a.m. is zero one hundred (0100) hours, two a.m. is zero two hundred (0200) hours, and so on until 11 p.m. which is 2300 hours.
After noon (1200 hours), to translate the regular time in the afternoon and evening, you simply add 12 hours to be within military standards. For instance, one p.m. is 1300 hours and five p.m. is 1700 hours.
Military Time Chart
Here's the whole list:
- Midnight (12:00 a.m.) — 0000 hrs
- 1:00 a.m. — 0100 hrs
- 2:00 a.m. — 0200 hrs
- 3:00 a.m. — 0300 hrs
- 4:00 a.m. — 0400 hrs
- 5:00 a.m. — 0500 hrs
- 6:00 a.m. — 0600 hrs
- 7:00 a.m. — 0700 hrs
- 8:00 a.m. — 0800 hrs
- 9:00 a.m. — 0900 hrs
- 10:00 a.m. — 1000 hrs
- 11:00 a.m. — 1100 hrs
- 12:00 p.m. — 1200 hrs
- 1:00 p.m. — 1300 hrs
- 2:00 p.m. — 1400 hrs
- 3:00 p.m. — 1500 hrs
- 4:00 p.m. — 1600 hrs
- 5:00 p.m. — 1700 hrs
- 6:00 p.m. — 1800 hrs
- 7:00 p.m. — 1900 hrs
- 8:00 p.m. — 2000 hrs
- 9:00 p.m. — 2100 hrs
- 10:00 p.m. — 2200 hrs
- 11:00 p.m. — 2300 hrs
For most daily things, military personnel uses local time as a reference. In order words, "report to duty at zero seven hundred (0700)," would mean you have to be at work at seven a.m., local time.
"The Commander wants to see you at fifteen hundred (1500) hrs," means you need to be in the Commander's office at three p.m., local time. When using local time, the Military observes Daylight Savings Time, if recognized by the state or country that the base is located in.
Designating Time Zones
Greenwich Mean Time
When it comes to operational matters (such as communications, training exercises, deployments, ship movements aircraft flights, etc.), the military must often coordinate with bases and personnel located in other time zones.
To avoid confusion, in these matters, the military uses the time in Greenwich, England, which is commonly called Greenwich Mean Time (GMT).
The U.S. Military refers to this time zone as Zulu Time, and they attach the "Zulu" (Z) suffix, to ensure the time-zone referred to is clear.
For easy reference in communications, a letter of the alphabet has been assigned to each time zone. The timezone for Greenwich, England has been assigned the letter "Z." The Military phonetic alphabet for the letter "Z" is "Zulu. The East Coast of the United States is denoted with the R letter (Romeo).
For example, a military message or communication might state, "The ship will cross into the area of operations (AOO) at 1300Z." That means the ship would arrive in the AOO when it is one p.m. in Greenwich, England. Where this gets confusing is when you have to translate to the current time in your location. The East Coast of the United States is five hours later than Greenwich Mean Time. So, 1300Z at GMT is the same as 0800 on the East Coast.
Daylight Savings Time
To make it even more confusing, the number changes when the United States observes Daylight Savings Time (DST). So, instead of five hours later than Greenwich Mean Time, the East Coast of the United States during the months of March (second Sunday) and November (first Sunday) the time difference will be six hours. The East Coast of the United States will be denoted with the Q letter (Quebec) during Daylight Savings Time.
International Date Line
Why does the military call this time "Zulu time?" You would think that the world could be divided equally into 24 one-hour equals a day.
However, due to the International Date Line (middle of Pacific Ocean), there are actually three more zones created and many of the zones are not exactly an hour apart (as the Sun travels). Some are only 30 to 45 minutes apart. But, somehow the system works as it is used mainly by ocean-going commerce vessels and the world's Navies.