What time is it right now? Go on, look at the clock… what does it read? Depending on what time of day you’re reading this, you probably followed up the time with a quick abbreviation; AM or PM. That’s because most of us (depending on where we live) use the base 12 system, separating our days into mornings (before noon) and evenings (afternoon). The 24-hour clock is vastly different though. In this clock, there is no “9 o’clock” or “6 pm”. No, instead, this clock simply reads the numbers as they appear. Here; I’ll explain!
There are 24 hours in a day (well, actually 23 hours 56 minutes, and 4.1 seconds to be exact) and the timer starts at a big fat zero. From there, all you need to do is read the number as it appears. If it’s 1 am, you will read 0100 hours (or) zero one-hundred hours. See, pretty simple isn’t it.
But what came first; the 24-hour clock or the base 12 system? Why did we change from one system to another? And who uses what method, and why?
What Came First
The first people to start using time recording techniques were the Egyptians, who made crude sundials that that utilized the base 12 system, which is why the day is divided into 12 parts.
Interesting Facts: The base 12 system (also known as the duodecimal system) as utilized in Ancient Egypt (as well as many other ancient civilizations) became popular for the ease of counting by hand, using the three sections on each finger, not including the thumb.
At night they used what is known as water clocks, to record the 12 night-time hours. They also liked to use the stars as they passed over the horizon, to determine the passage of time. This effectively divided the day into 24 ‘equal’ hours, that were counted in two separate 12-hour intervals. This is why time was initially recorded in two twelve hour segments.
And this was okay for a while, but dividing daylight into 12-hours would mean hour lengths would shift dramatically depending on what time of the year it was. Summertime hours would seemingly last forever, while winter-time hours would all but be gone in an instantaneously. This would become a major problem as we started traveling globally. At which point we needed hours, seconds and minutes to have precise measurements. Enter the 24-hour clock.
This piece discussing the history of the military time shows you how important the 24-hour clock is for today’s troops. But why was it invented, to begin with?
As time went on, and we became better equipped to tell the passage of time, the 24-hour clock became a more practical method. Since it was a direct correlation to the time of day, it proved to be much easier to calculate the duration of time. Even better, we could finally get rid of the superfluous labels of “ante meridiem” and “post meridiem.”
Benefits of the 24-hour Clock
The benefits of this clock are bountiful, not only does it do away with the A.M. P.M. monikers, but it gives actual calculations for each hour. Plus it actually tells you what hour of the day you are in. Whereas, the 12-hour systems pretend that the ‘12’ equals zero, which is why we have to use terms like ‘midnight’ and ‘noon.’ But even this can be super confusing, I mean to this day there is still debate on how to utilize the terms properly.
For instance when saying something like, “be there at midnight Tuesday.” It can be confused as meaning to be there on Tuesday starting at midnight, or to be there on the midnight that is occurring at the end of Tuesday? Who knows.
Of course, the 24-hour clock doesn’t have these issues because the days are marked clearly with a 00:00 to begin the day, and 23:59 to end it – although 24:00 is also an acceptable use. Furthermore, it leaves little room to confusion about when something is taking place.
Time Zones and the 24-hour Clock
Even with the newfound ability to track time in exact increments worldwide, there was still some work that needed to be done. We had to implement a universal system that would allow you to know what time it was in England while being in New York. That is when time zones became a necessity.
Before time zones were officially created on November 18, 1883, every city had their own clocks, set to their own time. This tended to cause mass confusion for international travelers, making it imperative that the world set a standard time. So, in 1884, time zones were implemented and Greenwich, England was selected to be the center of World Wide time.
This was chosen as the “Prime Meridian” because it is where the east longitudes meet the ‘west longitudes. Although the line is somewhat arbitrary and many argue that it could have been placed anywhere in the world.
But, because the US had already used it as the basis for their time zone, and more than 70% of the world already relied on Sea-charts that used Greenwich as the Prime Meridian; it became the official center of the world.
Understanding Time Zones
Most of us understand how time zones work in the states on our 12-hour system. There are four separate time zones for the continental US (Eastern, Central, Mountain, Pacific) and two more for Hawaii and Alaska (both named after the state). If it’s 1 PM Eastern Standard Time, that means it is 10 AM Pacific Standard Time. Not too difficult.
But it works a bit differently when using the 24-hour clock.
Rather than using the UTC that 12-hour clocks use, the 24-hour clock correlates to the phonetic alphabet and is based on the Greenwich Timeline or the Prime Meridian. So, 6:15 pm EST (Eastern Standard Time) would read as 18:15R. You can find the timezone you’re in here.
Essentially, each time zone to the east of Greenwich equals one letter in the alphabet. Time.unitarium.com has a useful table to help you visualize it a little better.
Where are 12-hour Clocks Still Used
Great Britain’s love of colonization is directly responsible for the vast majority of the 12-hour clock adopters – although, they have made the switch to 24-hour instead. So who still uses this system?
The United States, most of Central America, Saudi Arabia, Australia, and a few other countries are still on the AM/PM cycles, while the rest of the world (with the exception of a few countries who use both) are onto the 24-hour cycle.
Additionally, you’ll still see most analog clocks utilizing two 12-hour cycles as well. Although, this is mostly for aesthetic purposes, as 24 ticks are cluttery and don’t allow much room for recording minutes and seconds.
24-Hour Clock and Military Time
In most English speaking countries, civilians still use the 12-hour cycle, while the military uses still uses the 24-hour clock. Hence, the reason we call it military time America, but, there’s no difference at all.
Why do they use the 24-hour clock? Mostly this is to avoid confusion, but it’s also useful for keeping your troops honest.
Imagine leaving afternoon formation and being told that you had physical training the next day at 4:30. Now, the last thing you want to do is wake-up before 4 am and drag yourself to work to go running for 5 miles. So you (in your infinite wisdom) decide to pretend you thought you Staff Sergeant meant 4:30 in the afternoon. Brilliant right? You can see how using military time can make a difference here.
Okay so, this is just a silly byproduct of using military time, albeit a very effective one. The real reason is that the military is often conducting missions with people spanning multiple time zones and the 24-hour clock eliminates any clutter and confusion the 12-hour clock can cause.
Calculating 24-hour Clock
A lot of people have a difficult time when they first start learning how to tell military time, but it’s really very simple. Just take whatever the time is at the moment you look at the clock and add 12 to it – but only if its the afternoon. So if it’s 3:15 now, then in military time it is 15:15.
And yeah, it can be a bit of a hassle in the beginning, but after a while, you have to do any math at all. 16:00 will just be 16 hundred to you, and there will be no need to think any further. It’s like when you learn a new language, once you’ve become fluent in it, you no longer have to translate the words into their English meanings. At that point, the words just mean what they mean.
Wrap – Up
Okay, so now we know what type of clock came first (however rudimentary it was), and why we needed to use the 24-hour clock. We’ve figured out how the time-zones work with the 24-hour clock. And we’ve even gotten some practice in converting our 12-hour time to the 24-hour time and using the corresponding 24-hour clock time zones.
What interesting anecdotes do you have about the 24-hour clock and the history of it? Letting us know in the comment section below.