Have you ever wondered what people meant when they used 1700 military time or 2100 military time? Why are there more than 12 numbers used by the military anyways? The key to remember is that in the heat of battle, there is no room for errors, and a 24-hour clock helps military branches stay in better communication when it matters most. From converters to the history of its use, learn more about military time and why it’s so important.

Read next:

Have a Pulse? The Military Wants YOU!

Military Time Chart

The first thing to note is that when reading military time, you’ll need to use the full range of the 24 hours in a day. Where a civilian clock will begin at midnight (12:00 a.m.) and then go until noon (12:00 p.m.) before reusing the same numbers, military timekeeping does not. It’s easy to see how, even with this example, the use of 12:00 can create a potential for confusion in the military, even with the use of a.m. and p.m. This is why military time helps clear up discrepancies. A military time chart can help you convert civilian time into military time with ease. Beginning at midnight (0000) and working your way forward, you’ll see that once you hit 1:00 p.m., you’ll abandon the idea of repeating previous numbers and instead use 1300. So, 2:00 p.m. would be 1400, 3:00 p.m. is 1500, and so on and so forth until reaching 2359. Here's a simplified chart on how to use and tell military time:

Why It’s Used

Military times focus on a 24-hour clock rather than a clock focusing on two 12-hour halves. While adding yet another method of telling time may feel counterproductive on the surface for clearing up communication, because communication is of vital importance on the battlefield, having a system that doesn’t leave room for error can save time and lives. Using a military time converter can help civilians not accustomed to telling military time quickly reference the time in question for easy conversion. Another thing that helps civilians and those unaccustomed to the 24-hour clock is to look at it in a way that aligns with what they know: in a normal clock format, like the chart below.

A Brief History of Military Time

Have you ever asked yourself, “Why are there 24 hours in a day?” There have been archaeological finds tracing back all the way to the Ancient Egyptians that help answer this question. Found on a coffin lid known as the Diagonal Star Table, it’s the oldest known example of a 24-hour clock, adding yet another mathematical marvel to Egypt’s esteemed scientific history. One of the biggest differences found in the Egyptian system is that their civilization used temporal hours, which measure how much light there is at a certain point during the day. This would mean that hours were not equal in length and would change from day to day and season to season in order to maintain a balance between day and night. But a much more recent historical event is why the American Armed Forces use a 24-hour clock for military time. During World War I, the British Royal Navy used a 24-hour clock in 1915. This switch would inspire other Allied armed forces to do the same, including Britain’s Army in 1918. The first American branch of the military to use a 24-hour clock was the United States Navy in 1920. Furthermore, the U.S. Army wouldn’t use such methods until 1942 during World War II, continuing the trends seen with military forces getting on the same page due to the globalization of warfare. Though some nations that use 24-hour clocks have had their citizens adopt them, Americans have not been among them. There are some institutions outside of the military, such as first responders, who may rely on such clocks to help avoid communication issues. For now, the 24-hour clock is still referred to by millions of Americans as military time for a reason. With exceptions being few and far between, such timekeeping is typically still reserved for those enlisted in the American Armed Forces.

Suggested read:

3 Best Cheap Stocks To Buy Now Before Retiring From the Military