The 24-hour clock is a way of telling the time in which the day runs from midnight to midnight and is divided into 24 hours, numbered from 0 to 24. It does not use a.m. or p.m. This system is also referred to (only in the US and the English speaking parts of Canada) as military time[1] or (only in the United Kingdom and now very rarely) as continental time. In some parts of the world, it is called railway time. Also, the international standard notation of time (ISO 8601) is based on this format. A time in the 24-hour clock is written in the form hours:minutes (for example, 01:23), or hours:minutes:seconds (01:23:45). Numbers under 10 have a zero in front (called a leading zero); e.g. 09:07. Under the 24-hour clock system, the day begins at midnight, 00:00, and the last minute of the day begins at 23:59 and ends at 24:00, which is identical to 00:00 of the following day. 12:00 can only be mid-day. Midnight is called 24:00 and is used to mean the end of the day and 00:00 is used to mean the beginning of the day. For example, you would say "Tuesday at 24:00" and "Wednesday at 00:00" to mean exactly the same time. However, the US military prefers not to say 24:00 - they do not like to have two names for the same thing, so they always say "23:59", which is one minute before midnight.  24-hour clock time is used in computers, military, public safety, and transport. In many Asian, European and Latin American countries people use it to write the time. Many European people use it in speaking. Many digital wristwatches and clocks can display the time of day using the 24-hour clock. In railway timetables 24:00 means the end of the day. For example, a train due to arrive at a station during the last minute of a day arrives at 24:00; but trains which depart during the first minute of the day go at 00:00. To write shop opening hours until midnight use, for example, "00:00–24:00", "07:00–24:00". Advantages over the 12-hour clock system:
References
Page 2The 12-hour clock is a way of dividing the 24 hours of the day into two sections. The two halves are called ante meridiem (a.m.) and post meridiem (p.m.). Both names are from Latin, and numbered from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. Time from midnight to noon is a.m. and from noon to midnight p.m. The table at right shows how it relates to the 24-hour clock.
Normally time is shown as Hours:Minutes There are 24 Hours in a Day and 60 Minutes in each Hour.
Example: 10:25 means 10 Hours and 25 Minutes There are two main ways to show the time: "24 Hour Clock" or "AM/PM": 24 Hour Clock: the time is shown as how many hours and minutes since midnight. AM/PM (or "12 Hour Clock"): the day is split into:
Like this (try the slider): measure/images/time-am-pm.js
*Is that spelled "Meridiem" or "Meridian"? See here. Converting AM/PM to 24 Hour ClockAdd 12 to any hour after Noon (and subtract 12 for the first hour of the day): For the first hour of the day (12 Midnight to 12:59 AM), subtract 12 Hours Examples: 12 Midnight = 00:00, 12:35 AM = 00:35 From 1:00 AM to 12:59 PM, no change Examples: 11:20 AM = 11:20, 12:30 PM = 12:30 From 1:00 PM to 11:59 PM, add 12 Hours Examples: 4:45 PM = 16:45, 11:50 PM = 23:50 For the first hour of the day (00:00 to 00:59), add 12 Hours, make it "AM" Examples: 00:10 = 12:10 AM, 00:40 = 12:40 AM From 01:00 to 11:59, just make it "AM" Examples: 01:15 = 1:15 AM, 11:25 = 11:25 AM From 12:00 to 12:59, just make it "PM" Examples: 12:10 = 12:10 PM, 12:55 = 12:55 PM From 13:00 to 23:59, subtract 12 Hours, make it "PM" Examples: 14:55 = 2:55 PM, 23:30 = 11:30 PM Comparison ChartHere is a side-by-side comparison of the 24 Hour Clock and AM/PM:
Midnight and Noon"12 AM" and "12 PM" can cause confusion, so we prefer "12 Midnight" and "12 Noon". What Day is Midnight?Midnight has another problem: there is nothing to tell us "is this the beginning or ending of the day".
Imagine your friends say they are leaving for holiday at "midnight" on 12th March, what day should you arrive to say goodbye? Do you get there on the 11th (assuming they leave at the very start of the 12th), or the 12th (assuming they leave at the end of the 12th)?
It is better to use:
which the railroads, airlines and military actually do. So, when you see something like "offer ends midnight October 15th" tell them to use one minute before or after so there is no confusion!
Should "AM" be "ante meridiem" or "ante meridian" (likewise for PM)? The official (according to an American, Australian and British dictionary), and most common, spelling for AM is "ante meridiem" which is a Latin phrase. I recommend that spelling! But people sometimes use the phrase "ante meridian" (a "meridian" in this case refers to an imaginary line in the sky when the sun is at its highest point). 3698, 3699, 3700, 3701, 3702, 3703, 3704, 3705, 3658, 3660 Copyright © 2021 MathsIsFun.com |
What time is 23.00 in 12-hour clock?
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