Military time and it can be hard to understand, especially in regards to the numerous locations and time zones that exist, as well as complications with Daylight Savings Time. The common way of telling time, where five hours after noon is called ‘five p.m.’ is not used in military time. Instead, if it’s five p.m in Texas, you’re more likely to hear it called something like “Seventeen hundred Sierra” or, even more confusingly, “Twenty-three hundred Zulu”. What is going on here?
This article will help you make sense of Military Time Zones and how they work with Daylight Savings Time. Soon, you’ll understand military time references without any confusion! Read on to find out how.
A History of Military Time
When military people communicate with each other, they need to be understood clearly, often for the very first time. The message must be unambiguous and have one meaning only. Stated simply, an order to “attack Target B at 5 p.m” must never be confused with an order to attack “Target D at 5 a.m”. The consequences of such miscommunication could be disastrous.
As such, it is easy to see why militaries decided to adopt a twenty-four hour standard clock so that no time of the day could be confused with any other time of day, similarly to how the NATO phonetic alphabet ensures that letters that sound similar are not misheard for each other. Military times are thus always referred to in a standardized way, such as “seventeen hundred thirty” for 17:30 or 5.30 p.m, or “zero zero fifty-three” for 0:53 or 12.53 a.m. This is different from a 24-hour clock in that military time doesn’t use a colon to separate hour and minute, and that the time is pronounced the same way on each occasion.
The British Royal Navy was first to begin using this time system, in 1915. In 1942, shortly after entering World War Two, the United States Army adopted this time system too. Therefore, next time you watch a film where the commanding officer issues an order telling troops to be ready at “zero eight hundred hours”, you will see you’ve grasped the first part of this puzzle.
Time Zones and the NATO Phonetic Alphabet
With the advent of modern telecommunications and high-speed long-distance travel by train, automobile, and airplane, it became necessary to begin referring to time zones in everyday speech. For example, if you live in Los Angeles and plan to call your aunt in Philadelphia on the telephone, you’ll already be familiar with this quandary. Should you tell her you’re phoning at 4 p.m your time? Or at 8 p.m her time? How do you decide?
Now, imagine this scenario in a much more tense, fast-paced, life-or-death setting, while communicating with a foreign military officer who may or may not know what time zone you’re currently in. This person may not speak English as a first language, either. What you and the other officer both need to ease the tension is a standard in common.
Greenwich Mean Time
You’ve probably heard of GMT before, an initialism standing for Greenwich Mean Time. You may even have heard of its scientifically official name, UTC (Coordinated Universal Time, with words in French grammatical order). But what is this time zone and what does it have to do with Greenwich?
In order to understand this, you must consider that sailors throughout history didn’t have a way of calculating their longitude, and as a result, their position east or west in the world. Latitude was easily determined by looking at the angle of the sun, but figuring out one’s longitude was best done on land, from the comfort of home, over several weeks. Numerous methods were proposed between the 1500’s to 1900’s, and even today, ships tend to carry multiple backup systems to calculate longitude in case their GPS systems fail.
There also isn’t any point of reference that would represent an obvious ‘zero’ longitude line as there is the equator for zero latitude. In 1851, Sir George Airy proposed that the Greenwich Observatory in London should be the point of zero longitude, and in 1884, twenty-five nations voted to use Airy’s proposition as their accepted line of zero longitude. Since then, this line, known as the ‘prime meridian’, has been called Greenwich Mean Time. Radiating outwards from this defined center, every fifteen degrees represents one hour of time difference. You may also wonder what is on the ‘other’ side of this line, or the point of 180 degrees west or east, and this is known as the International Date Line, because it is the point where one calendar day ‘blends into’ the next.
So, what does any of this have to do with military time? The answer is that the military, requiring a standard zone to avoid confusion, also uses the GMT or UTC standard time as a zero reference point, but they refer to it with the name of ‘Z’. In the NATO phonetic alphabet, this time zone is then called ‘Zulu’. Now, the two officers who speak different languages can still refer to times in ‘Zulu time’ and have no confusion. If you want to refer to a specific time zone using military conventions, you can do this also.
Naming Specific Time Zones
Conveniently, there are a similar number of letters in the English alphabet as there are major time zones (25), so each letter can stand for one time zone, with one letter left out. The military chose to leave J out because of its visual similarity to I, and because some international alphabets don’t have a character to represent ‘J’. You may also be aware that there are some ‘minor’ time zones that are half an hour offset from major zones, and the military solution for this is to include a star character, *, after the alphabet letter, to represent the offset zone.
The map above shows the standard time zones, with zone 0 in the center representing Z time. Ascending eastward, +1 is A, +2 is B, +3 is C, +3.5 is C*, and so on, all the way to M for +12. Meanwhile, heading westward from the center, the zones go -1 for N, -2 for O, -3 for P, all the way to -12 for Y.
If all of this sounds like it may be a bit much, here are some examples to check your understanding. The examples include local and Z-reference times:
- How would you say 5 p.m in California standard time? (1700 Uniform / 0100 Zulu)
- How would you say 2.30 a.m in New York standard time? (0230 Romeo / 0730 Zulu)
- How would you say 12 p.m in Iran standard time? (1200 Charlie *Star / 0830 Zulu)
If you have made it this far, you have understood two out of three of the major components to military time!
The Military and Daylight Savings Time
The final aspect to be considered about military time is the introduction of Daylight Savings Time, which was conceptualized in 1895 and first used in 1908. In 1916, while at war, the German Empire was the first nation to adopt it across its country, and by 1918, the United States had done so too. In the US, this was a political issue that went back and forth many times. In 1967, finally, the proponents of DST were successful at having it implemented, and as of today, all states except Hawaii and Arizona observe Daylight Savings Time.
For the unfamiliar, DST is the practice of setting clocks an hour forward in March and an hour backward in November, effectively making summer sunrises and sunsets an hour later on the clock than winter sunrises and sunsets. The exact date to set the clocks backward and forward varies year by year, and is standardized by each country. This practice, favored by retail interests, is observed in most of North America and Western Europe, but generally ignored by Asia and Africa. Therefore, military bases that are located in areas that use DST observe it, while ones located elsewhere do not.
The way the military observes DST is by changing their clocks in areas that utilize DST, and by referring to the new time zone letter during times that DST is active. For example, most of Texas is in UTC -6 during winter (its standard time) and UTC -5 during summer (its ‘savings’ or adjusted time). The corresponding military time zone codes for Texas are thus Sierra (standard, from November to March) and Romeo (adjusted, from March to November). This ensures that military time corresponds with local time, while staying faithful to Zulu time by still using the same conversion calculation.
To recap, military time is composed of three parts:
- A twenty-four hour clock, expressed by four digits with no colon to separate them, where leading zeros are pronounced, and double trailing zeros are pronounced as ‘hundred’;
- A letter code to show time zone, from ‘Alpha’ to ‘Zulu’, except J, and where’ Zulu’ time corresponds to UTC or GMT – the local time in London, which is a standard reference point in international communication;
- Letter code changes in areas that observe Daylight Savings time while DST is active.
The standard time 5 p.m in Texas can thus be written as (and spoken of as):
1700S (“Seventeen hundred Sierra”) for local communication;
2300Z (“Twenty-three hundred Zulu”) for communication across time zones.
While military time is indeed complicated at a first glance, upon some reflection, so is timekeeping in general. For this reason, the military’s effort to make timekeeping unambiguous has plenty of useful applications outside of the military, such as in medicine, aviation, commerce, transport, computation, and countless others. Hopefully, this article has generated some interest and understanding around the concept of Daylight Savings time, and its impact on military time.