Military Time: How it Works
Sometimes using 12-hour clock notation can be confusing because of its ambiguity. It requires us to be really careful with the suffix it has which can be a.m. or p.m. depending on the time of a day: morning or evening. So, military time could be a solution to this problem since its main purpose is to make an interpretation of time as precise and definite as possible. In this case, we can avoid the risk of misreading the time.
The difference between military time and regular time
The regular time is based on the 12-hour clock format. In this system, the hours are counted from 1 to 12 and this cycle repeats twice during the day. These sequences are defined by suffixes a.m. for the first one (during the morning) and p.m. for the next one (in the evening).
On the contrary, military time is based on the 24-hour clock notion, which means using only one cycle during the day instead of two. After 12, instead of 1 p.m., it moves to 13 and continues up till 24 or 00.
Also, last but not least, originally in the military time, instead of minutes, the hundredths or decimal hours are used. This comes from decimal time which was supposed to give more precision and make it easier to fraction time. But nowadays, it is more common to see standard minutes used in military time1.
How military time works?
Some people are confused when they see “1535” or “0925” to refer to time. But in reality, it’s very simple. All you have to know is that two first digits stand for hours and another two digits represent minutes. From 1 a.m. until 9 a.m. it is needed to use leading zero, to keep all the numbers well organized and avoid any possibility of misinterpretation. Therefore, 1 a.m. in a military time will be 0100, 2 a.m. 0200, and so on. But what about after 12 a.m.? A 12-hour format clock will start the cycle again with the number 1 when the military time will keep going so that 1 p.m. in military time will be represented like 1300. Accordingly, 2 p.m. will be 1400 and so on, until we reach 11 p.m. (23 in military time). After 2359 (11:59 p.m.) the new day will begin with 0000 (in the 12-o’clock format it is 12:00 p.m.). If you still feel confused, you can take a look at the following tables:
Military time chart
|Regular time||Military time||How to say|
|1:00 a.m.||0100||Zero one hundred|
|2:00 a.m.||0200||Zero two hundred|
|3:00 a.m.||0300||Zero three hundred|
|4:00 a.m.||0400||Zero four hundred|
|5:00 a.m.||0500||Zero five hundred|
|6:00 a.m.||0600||Zero six hundred|
|7:00 a.m.||0700||Zero seven hundred|
|8:00 a.m.||0800||Zero eight hundred|
|9:00 a.m.||0900||Zero nine hundred|
|10:00 a.m.||1000||Ten hundred|
|11:00 a.m.||1100||Eleven hundred|
|12:00 a.m.||1200||Twelve hundred|
|1:00 p.m.||1300||Thirteen hundred|
|2:00 p.m.||1400||Fourteen hundred|
|3:00 p.m.||1500||Fifteen hundred|
|4:00 p.m.||1600||Sixteen hundred|
|5:00 p.m.||1700||Seventeen hundred|
|6:00 p.m.||1800||Eighteen hundred|
|7:00 p.m.||1900||Nineteen hundred|
|8:00 p.m.||2000||Twenty hundred|
|9:00 p.m.||2100||Twenty-one hundred|
|10:00 p.m.||2200||Twenty-two hundred|
|11:00 p.m.||2300||Twenty-three hundred|
|12:00 p.m.||0000||Zero hundred hours or Midnight|
The difference between 24 hours format and military time
At first glance, it may look like a 24 hours format and a lot of people refer to it as military time.
For instance, In some parts of the United States, the 24-hour format is referred to as military time. Some people can argue that it’s the same and there’s part of the truth to it, but it is not completely correct. First of all, the 24-hour format is based on military time, the concept is the same: dividing a day by 24 parts-hours. But still, there are some determining differences between them:
The difference in cycles
For example, although both formats are based on dividing the day into 24 hours, the 24-hour cycle begins at 00:00 and ends at 23:59. The military time begins its cycle at 0001 and finishes it at 2400. However, in June of 2015, the Department of the Navy published in their correspondence manual otherwise. The document mentions 0000 as a starting point and 2359 as the last minute of the day2.
The way of counting minutes
Probably, the most difficult part. In civil time, 1 hour contains 60 minutes, when in the military time originally it has 100 hundredths. Here you have a chart of civil minutes and military ones3:
Minutes to hundredths conversion chart
|Standard minutes||Hundredths||Standard minutes||Hundredths||Standard minutes||Hundredths|
How quickly tell military time
Some people are struggling to get used to military time or the 24-hour clock format. But it’s not as difficult as it may look at the beginning. All you have to do is to subtract 12 when the number of hours surpasses 12 because it is the moment where all complications come. For example, 1900 or 19:00. Minutes stay the same, so all we have to do is to subtract 12 from 19 and we get 7. Very simple. And if we have minutes, it still works the same. For example, 2345 or 23:45. Ignore minutes 23(45) and subtract 12 from 23, the result is 11. Now, let’s put the minutes back and we obtain 11:45.
In military time the midnight usually is expressed as 0000 or 2400. Sometimes it is used for schedules and you could see something like “00:00 to 24:00” when an establishment is open 24 hours.
How to convert 12-clock format time into a military time
But what about transforming the 12-clock format time into a military time? In this case, we should follow the same strategy with the only difference: instead of subtracting 12, we should add it. And, please note, we should add 12 ONLY if the suffix is p.m. In case, when the suffix is a.m., everything stays the same with the only difference that if the number of hours is from 1 to 9, we’ll have to add a leaping zero in front: 7:25 a.m. will be 0745 in military time. And when the suffix is a p.m. we should add 12 to hours. For example, 5:15 p.m., 5 plus 12 gives us 17. So, the military time for 5:15 p.m. will be 1715.
The way to pronounce and write
Another important difference is a way to pronounce and to write the time in the military format. In the 24-hour clock format, we use a colon to separate minutes from hours and it looks like 16:30, 18:45, and so on. But in military time, we don’t need to use a colon to divide the digits that stand for hours from digits that represent minutes. Therefore, it looks like 1633, 1845… And for hours from 1 to 9 we need a leading zero in front, so it looks like 0125, 0720, etc.
Also, these small differences in writing are followed with a distinct way to read the time. For example, 16:30 is read as “sixteen thirty” or “half past four” when 1630 is read as “sixteen thirty”. Also, in military time, when the number is “round” and isn’t followed by any minutes, we should read hours as hundred: for example, 1700 is read as “seventeen hundred”. In the 24-hour clock format, it would be written as 17:00 and pronounced as “seventeen” or “five o’clock”.
Pretty simple, right?
But what about the leading zero? It is quite easy as well. For example, 0930 should be read as “zero nine thirty”. And if the number is “round” like 0800, we should read it as “zero eight hundred”.
The use of military time
From what we can see, the military time or 24-hour clock format is more precise and helps to avoid any misinterpretation. Who at least once hasn't mistaken a.m. and p.m. when setting an alarm in the morning?
Because of the convenience of interpreting the time, the military format is very common around the world and widely used in a lot of industries, especially the ones that require it to be very precise.
The establishments that use military time
First of all, it is used in the military to refer to the time and when certain events are taking place.
Even in the regions that commonly use the 12-hour clock format, the nurses and healthcare establishments will go for 24-hour clock format as well. The reason for that is the precision that it gives to avoid any possible mistakes. All the patients’ medical history and all the appointments will be documented using the 24-hour clock format. It also helps nurses to know when to give the prescribed medicine to each patient and to keep track of all administered treatments4.
In the same way, police are required to use the 24-hour format clock for the documents, too. It’s because this system is more efficient and helps to avoid any possible mistake or wrong misinterpretation as it can happen with the 12-hour clock format.
Furthermore, the airports also use this format for the same reasons. But to minimize possible misinterpretation even more, they would avoid scheduling flights at midnight (12:00 p.m. or 0000) because it can mislead the passengers about the day of the flight. Is more common for the flights to be scheduled for 23:55 or even 23:59 which helps to clarify on which day the flight is.
Usage of military time around the world
Coordinated Universal Time is based on military time and uses 24-hour time notation. So this makes a military time universal around the world.
The majority of Europeans use military time because of its convenience. Although, colloquially people won’t use “at sixteen hundred” or “ at sixteen o’clock”. They still will say “at 4 o’clock” specifying whether it’s in the morning or in the evening.
Many countries from Latin America also decided to adopt this system. However, there are some countries that use both formats. Such as a majority of English speaking countries. In this case, the citizens of these countries will use the format they prefer, but official establishments such as police or healthcare are required to use the 24-hour format for all documentation and appointments.
Nowadays, military time is used all over the world. The only difference is that the United States uses an original military time when the rest of the countries will use a standard 24-hour clock format, separating hours from minutes with a colon and sometimes skipping the leading zero.
Military time zones
There are twenty-five military time zones. Each of them has a letter assigned which represents a time zone according to Coordinated Universal Time (UTC). The names are taken from the NATO phonetic alphabet which is commonly used in military and other authorities. However, J “Juliet” isn’t used here since it can be mistaken with “I”.
Usually, when the time is expressed in military time format, the letter that represents a certain time zone will stand at the end, for example, 1630H spoken as “sixteen thirty Hotel” or 1600G would be “sixteen hundred Golf” and so on.
The rest of the abbreviations and the time zones that they represent are shown in the chart below5:
|Abbreviation||Time zone name||Offset|
|A||Alpha Time Zone||UTC +1|
|B||Bravo Time Zone||UTC +2|
|C||Charlie Time Zone||UTC +3|
|D||Delta Time Zone||UTC +4|
|E||Echo Time Zone||UTC +5|
|F||Foxtrot Time Zone||UTC +6|
|G||Golf Time Zone||UTC +7|
|H||Hotel Time Zone||UTC +8|
|I||India Time Zone||UTC +9|
|K||Kilo Time Zone||UTC +10|
|L||Lima Time Zone||UTC +11|
|M||Mike Time Zone||UTC +12|
|N||November Time Zone||UTC -1|
|O||Oscar Time Zone||UTC -2|
|P||Papa Time Zone||UTC -3|
|Q||Quebec Time Zone||UTC -4|
|R||Romeo Time Zone||UTC -5|
|S||Sierra Time Zone||UTC -6|
|T||Tango Time Zone||UTC -7|
|U||Uniform Time Zone||UTC -8|
|V||Victor Time Zone||UTC -9|
|W||Whiskey Time Zone||UTC -10|
|X||X-ray Time Zone||UTC -11|
|Y||Yankee Time Zone||UTC -12|
|Z||Zulu Time Zone||UTC +0|
As you can see from the chart shown before, Z-time corresponds to the time on the prime meridian usually mentioned as Greenwich. So, to convert this time to your local one, you need to figure out which “offset” corresponds to the zone where you live. Based on that, you will have to subtract or add the difference your zone has with the 0 meridian which depends on whether you are located “ahead” or “behind” it.
History and origins of military time
Nowadays military time is used mainly to avoid any possibility of misinterpretation time and mistaking a.m. with p.m. and vice versa. All official authorities and especially spheres that require collaboration and communication with different countries from distinct time zones will use the 24-hour clock system. But in reality, this format had appeared a long time before these institutions even existed.
The military time started its existence many centuries ago. The first prototype was used in ancient Egypt. During the day, ancient Egyptians were using a solar clock that was divided into 10 sectors-hours. The shadow from the stick would show the time when it reached the sectors marked on the wall or floor. This simple construction helped them to determine the time throughout the day, but at night they were orientating in time by watching the stars. There were 36 groups of stars that would rise one by one with an interval of 40 minutes6.
The first mechanical 24-hour format clock was found in Italy. It was a complex mechanism that needed ropes to hit the strokes. The last one would happen at Midnight. Unfortunately, it required a lot of rope, therefore, later the amount and frequency of strokes had to be diminished7.
Also, the first person to propose the 24-hour format clock was Sir Sandford Fleming. He worked a lot to elaborate an optimal way of timekeeping and took part in developing Coordinated Universal Time. But the situation that made him come up with the idea of the 24-hour clock notion was quite trivial. In 1876, he missed a train because the ticket contained an error: instead of a.m. there was written p.m. This situation inspired the scientist to work on a new format so this type of mistake could be avoided in the future.
During the 20th century, a lot of European countries decided to implement this format after the government of Great Britain adopted a 24-hour clock format all over the country in 1893. It took almost 40 years for the United Kingdon to make this change official and it took several attempts to achieve it. Amongst the countries that followed this practice were France, Denmark and Greece. Within the next ten years, Spain, Portugal, Belgium, Switzerland, Turkey and Germany also had followed this system8.
Meanwhile, the rest of the world also started to consider changing their time format. Countries of Latin America, the United States and Canada started introducing a new system. First, they implemented it for the army and a couple of years later on a national level. In fact, some of these countries still use the 12-hour clock format and it’s more common amongst their citizens, as the case with the United States. Even some local channels will display time in both formats. However, all official establishments are required to use military time to avoid any possible misinterpretation. The airlines around the world also use this format9.
Military time in pop culture nowadays
Like anything that is a part of our daily routine, military time is not an exception and has its reflection in some aspects of our lives. For example, there is even a movie called “zero-dark-thirty” which is a common slang amongst military communities. This expression, which is the base of this film, in reality means the time after midnight at 12:30 a.m. or 0030 (zero-zero-thirty) in military time.
There are even more movies that contain some references for military time. Its use is more common for stories related to military, detectives or thrillers. For example, it is often used in the new comedy TV show “Space Force” streamed on Netflix.
Also, mankind tends to laugh about everything and military time wasn’t left without the attention of internet users.
Hector Vera (2009). “Decimal Time: Misadventures of a Revolutionary Idea, 1793–2008 ↩
Dohrn-Van Rossum, Gerhard (1996). “History of the Hour. Clock and Modern Temporal Orders.” The University of Chicago Press. p. 114. ISBN 0226155110 ↩
Clark Blaise (2000). “Time lord : Sir Sandford Fleming and the creation of standard time”. ISBN 9780297841364 ↩