15:00 – what does this unit of time mean, and how is it converted? Picture a hypothetical Wednesday: a shop owner in Spain has closed for midday siesta, an American elementary school student has boarded the bus home, and you’re likely ready for a third cup of coffee. T
he approximate time in each scenario is 15:00. We experience 15:00 every day, but how do we define it in context? How do we convert it into a 12-hour clock format? How does the meaning vary depending on global position?
15:00 – A Brief Summary
Pronounced “fifteen-hundred” (rather than one thousand five hundred), 15:00 is a unit of time that is based on the 24-hour clock. Relative to the 12-hour clock, 15:00 simply translates to 3:00 PM–a time of day recognized to mark the initial transition from afternoon to evening.
To better understand 15:00 as a unit of time, it must be placed into context. The 24-hour clock, or military time, is the most common system for telling time throughout the world. From midnight to midnight, 24 one-hour increments indicate one full day. The beginning of the day, midnight, is notated as 00:00, whereas the end of the day, just before midnight, is notated as 23:59. Therefore, 15:00 is the 15th hour in the day.
English speaking countries generally apply the 12-hour clock system of timekeeping. However, there are specific benefits to using the 24-hour system, indicated by the myriad of professional fields that prefer the system–notably the medical field, transportation systems, information technology, and of course, the military.
Benefits of using the 24-hour clock
- The 24-hour clock is less ambiguous. Rather than assigning the same number to two different times of day (e.g. 3 AM and 3 PM), the 24-hour clock assigns a unique number to each hour of the day. For some hours of the day, context clues help distinguish AM from PM, but for other times (e.g. 8 AM vs. 8 PM), the meaning can become more equivocal. By using the 24-hour clock (e.g. 8 AM vs. 20:00), the time of day is no longer open to interpretation.
- Many countries already use this system. Whether you are traveling for international business, vacation, or to visit friends and family, you will likely experience the use of the 24-hour clock abroad. Learning this system can simplify your international experience. Transportation (trains, buses, flights), events, and even conversations with locals are saturated with critical pieces of information: the time!
- Many professions use this system. For example, medical professionals use this system so that the time a patient received medical care is clear, and the military uses it for precision and punctuality. My job as a U.S. Forest Service ranger uses it so that there is no room for interpretation regarding backcountry check-ins, and to relay messages to the district dispatch office.
A more in-depth history of the 24-hour clock can be found here.
15:00 – How to Convert Between Military Time and a 12-hour Clock
While studying abroad in college, my host sister and I once made plans to meet up for a kickboxing class. She said, “meet me at fifteen.” In my head, I scrambled to convert Italian to English, and subsequently to convert from a 24-hour clock to a 12-hour clock. If you grew up keeping time via the 12-hour clock system, then you’ve likely experienced a similar feeling of arithmetic chaos. Knowing how to convert from a 24-hour to a 12-hour clock efficiently in your head can save you from unnecessary headaches in the future.
To convert from a 12-hour clock to a 24-hour clock:
Add 12 to times denoted by PM. The time is 3 PM. 3 + 12 = 15 = 15:00. Pretty simple, right? Give it a try.
1. What is 5 PM in military time? (Answer: 5 + 12 = 17 = 17:00)
2. What is 11:15 PM in military time? (Answer: 11.15 + 12 = 23.15 = 23:15)
3. What is 12:00 AM in military time? (Answer: 00:00, the day starts over at midnight.)
To convert from a 24-hour clock to a 12-hour clock:
- Subtract 12 from times denoted by PM. This method is essentially the opposite of what we did above. The time is 15:00. 15 – 12 = 3 = 3 PM.
- Subtract 2 from the second digit of the hour for times denoted by PM. The key here is to ignore the first digit after you subtract 2. The time is 15:00. 15 – 2 = 13 (ignoring the first digit) = 3 PM. Note that 22:00/10:00 PM is the exception to this rule.
1. What is 13:22 in non-military time? (Answer: 13.22 – 2 = 11.22 (ignore the first digit) = 1:22 PM or 13.22 – 12 = 1.22 = 1:22 PM)
2. What is 18:50 in non-military time? (Answer: 18.50 – 2 = 16.50 (ignoring the first digit) = 6:50 PM or 18.50 – 12 = 6.50 = 6:50 PM)
3. What is 22:02 in non-military time? (Answer: 22.02 – 2 = 20.02 = ? (the exception) or 22.02 – 12 = 10.02 = 10:02 PM)
The chart below can also be used as a reference. To use the chart, decide whether you are converting from a 12-hour clock to a 24-hour clock, and find the time you wish to convert from in the proper column.
15:00 – Latitude, Longitude, & Time Zones
“Time is the longest distance between two places.”
― Tennessee Williams, The Glass Menagerie
Now that we’ve developed a foundation for understanding the 24-hour clock, we can better grasp the meaning of time depending on global position. Latitude refers to locations that run from north pole to south pole, or vertically (think ‘ladder’), while longitude refers to locations that run parallel to the equator, or horizontally (think ‘rungs of a ladder’). Combinations of latitude and longitude, or coordinates, determine a specific geographic location on earth. These locations are different in nature because of the interactions between varying global factors–curvature of the earth, distance from the sun, atmospheric conditions, etc. That means depending on your geographic location, you not only experience 15:00 differently than other time zones, but other global positions as well.
Based on the scenarios presented at the beginning of this article, a Spanish shop owner taking a siesta and an American elementary school student riding the bus home, you can use this interactive map to show 15:00 in Barcelona, Spain and Seattle, Washington on any calendar date. These maps also show the relative position of the sun and the moon at 15:00. For reference, UTC time–the most common time standard across the world– is shown as well.
Like all other units of time, not only is the time 15:00 affected by time zones and sun position but geographic location as well.
If it’s 15:00 UTC – what time is it in other time zones?
Coordinated universal time (UTC), based on Greenwich mean time, is denoted by UTC + 0. To figure out what time it is in another time zone, we can use the Standard Time Zones of the World map below. To use this map, first determine what time zone/country you are interested in. Let’s stick to Barcelona, Spain and Seattle, Washington. If it’s 15:00 UTC, what time is it in Seattle? On the map, Seattle falls into the PST – 8. This means we subtract 8 from UTC time, 15 – 8 = 7:00. Barcelona falls in the UTC + 0 timezone and therefore has a time of 15:00 as well.
Military Time Conversion – Tips & Tricks
If you were raised using 12-hour timekeeping, it can take a jumble of math (wait, I have to do math in real life?) and thought before you get a feel for what terms like 15:00 mean. If you’re interested in making 24-hour clock conversions second nature, give these tips and tricks a go.
- Change the time on your smartphone. According to Deloitte’s Global mobile consumer survey: US edition, the average American checks their smartphone 52 times a day. That’s 52 opportunities to ‘rewire’ your brain to think in military time, in a simple, passive way that requires little effort. To change the time on your iPhone from a 12-hour clock to a 24-hour clock, use this pathway: Settings -> General -> Date & Time -> 24-hour Time. To learn how to change the time on your Android, click here.
- Give specific military times concrete associations. If the ‘subtract 12’ trick mentioned above seems a little daunting, try making time associations with events in daily life and use them as a reference point. For example, I work for the forest service– a government organization that uses the 24-hour clock for timekeeping. An average workday ends at 16:00, or 4:00 PM. Each day at 16:00 I have to ‘sign out’ for the day and write down the time. Because of this, I now have an association for 16:00 and I can use it as a reference when converting other times in my head. See, if I know 16:00 = 4:00 PM, then when offered 18:00 as a time, I can compare 18:00 to 16:00 and gather that 18:00 = 6:00 PM quicker than by using the ‘subtract 12’ trick. Try making a concrete association for 15:00.
- Make flashcards. It may sound silly, but learning a concept like the 24-hour clock calls for rote memorization. If tricks 1 and 2 don’t work for you, buckling down and studying is a helpful alternative. Using smartphone flashcard apps are a technological alternative. Practice makes perfect!
Understanding the 24-hour clock is a feat that takes time, patience, and practice. By understanding the meanings and conversions of specific times, we are one step closer to mastering the process. The 24-hour clock is a helpful tool to avoid general ambiguity and headaches while traveling. It is also used by a plethora of professions as the standard way of timekeeping. Conversions are made easier by using the ‘add 12’, ‘subtract 12’, and ‘subtract 2’ rules, and understanding geographic location can give you a better feel for military time and time zones. Changing the time on your smartphone, creating concrete associations for specific times, and making flashcards are additional tools to help you become a military time expert. We experience 15:00 every day, no matter our global position. Outside of meanings and conversions, what does 15:00 mean to you?