Time - AM/PM vs 24 Hour Clock

Ordinarily time is shown every bit Hours:Minutes

In that location are 24 Hours in a Day and threescore Minutes in each Hour.

Example: x:25 means 10 Hours and 25 Minutes

Showing the Time

There are ii main ways to show the time: "24 60 minutes Clock" or "AM/PM":

24 Hour Clock: the fourth dimension is shown as how many hours and minutes since midnight.

AM/PM (or "12 Hr Clock"): the day is split into:

  • the 12 Hours running from Midnight to Noon (the AM hours), and
  • the other 12 Hours running from Noon to Midnight (the PM hours).

Like this (try the slider):

measure/images/fourth dimension-am-pm.js

day am pm

AM

PM

Ante Meridiem*
Latin for "before midday"

Post One thousanderidiem*
Latin for "afterward midday"

Midnight to Noon

Noon to Midnight

24 Hour:
00:00 to xi:59

24 Hour:
12:00 to 23:59

*Is that spelled "Meridiem" or "Elevation"? See hither.

Converting AM/PM to 24 Hour Clock

Add 12 to any hr after Noon (and subtract 12 for the first hr 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 i:00 AM to 12:59 PM, no change

Examples: 11:xx AM = 11:20, 12:30 PM = 12:thirty

From 1:00 PM to 11:59 PM, add 12 Hours

Examples: 4:45 PM = xvi:45, 11:50 PM = 23:50


Converting 24 Hour Clock to AM/PM

For the commencement 60 minutes of the day (00:00 to 00:59), add 12 Hours, make information technology "AM"

Examples: 00:x = 12:10 AM, 00:40 = 12:40 AM

From 01:00 to 11:59, but make information technology "AM"

Examples: 01:xv = 1:xv AM, xi:25 = eleven: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 = eleven:30 PM

Comparison Nautical chart

Here is a side-by-side comparison of the 24 Hour Clock and AM/PM:

Case: on the hour


Example: 10 minutes past

24 Hr Clock

AM / PM

24 Hour Clock

AM / PM
00:00 12 Midnight
00:10 12:10 AM
01:00 i:00 AM 01:10 i:ten AM
02:00 2:00 AM 02:10 two:ten AM
03:00 three:00 AM 03:10 3:10 AM
04:00 iv:00 AM 04:ten 4:10 AM
05:00 five:00 AM 05:10 5:10 AM
06:00 6:00 AM 06:10 half-dozen:10 AM
07:00 7:00 AM 07:10 7:10 AM
08:00 viii:00 AM 08:10 8:10 AM
09:00 9:00 AM 09:10 ix:10 AM
ten:00 10:00 AM 10:10 x:10 AM
11:00 11:00 AM xi:10 11:ten AM
12:00 12 Noon 12:x 12:10 PM
13:00 1:00 PM 13:ten 1:10 PM
xiv:00 two:00 PM fourteen:10 2:x PM
fifteen:00 iii:00 PM 15:10 3:10 PM
xvi:00 4:00 PM 16:10 iv:ten PM
17:00 five:00 PM 17:10 5:10 PM
xviii:00 six:00 PM xviii:10 6:ten PM
nineteen:00 7:00 PM 19:10 seven:10 PM
20:00 eight:00 PM xx:10 8:10 PM
21:00 nine:00 PM 21:10 nine:ten PM
22:00 10:00 PM 22:ten ten:10 PM
23:00 11:00 PM 23:ten 11:10 PM

Midnight and Noon

"12 AM" and "12 PM" can cause confusion, and so nosotros 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 solar day".

holiday

Imagine your friends say they are leaving for holiday at "midnight" on 12th March, what day should you arrive to say goodbye?

Practise you go there on the 11th (assuming they leave at the very start of the 12th), or the 12th (assuming they leave at the stop of the 12th)?

It is better to use:

  • 11:59 PM or 12:01 AM, or
  • 23:59 or 00:01 (24-Hour Clock)

which the railroads, airlines and military machine actually practise.

And so, when you see something like "offer ends midnight October 15th" tell them to utilize one minute earlier or after so there is no confusion!

Footnote on "Meridiem" vs "Elevation"

Should "AM" be "ante meridiem" or "ante meridian" (likewise for PM)?

The official (co-ordinate to an American, Australian and British dictionary), and nearly mutual, spelling for AM is "dues meridiem" which is a Latin phrase. I recommend that spelling!

But people sometimes use the phrase "dues meridian" (a "peak" in this case refers to an imaginary line in the sky when the dominicus is at its highest point).

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