Time - AM/PM vs 24 Hour Clock

Normally time is shown as Hours:Minutes

There are 24 Hours in a Day and lx Minutes in each Hour.

Case: 10:25 means ten Hours and 25 Minutes

Showing the Time

There are ii master means to show the time: "24 Hour Clock" or "AM/PM":

24 Hour Clock: the time is shown every bit how many hours and minutes since midnight.

AM/PM (or "12 Hour Clock"): the twenty-four hours is separate 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).

Similar this (try the slider):

mensurate/images/time-am-pm.js

day am pm

AM

PM

Ante Meridiem*
Latin for "before midday"

Post Meridiem*
Latin for "after midday"

Midnight to Noon

Noon to Midnight

24 Hr:
00:00 to eleven:59

24 Hr:
12:00 to 23:59

*Is that spelled "Meridiem" or "Tiptop"? See here.

Converting AM/PM to 24 Hour Clock

Add 12 to any 60 minutes after Noon (and decrease 12 for the commencement 60 minutes of the mean solar day):

For the first hour of the twenty-four hours (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: xi:20 AM = 11:20, 12:30 PM = 12:thirty

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

Examples: iv:45 PM = 16:45, 11:50 PM = 23:l


Converting 24 Hour Clock to AM/PM

For the first 60 minutes of the mean solar day (00:00 to 00:59), add 12 Hours, make it "AM"

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

From 01:00 to 11:59, only make it "AM"

Examples: 01:15 = 1:15 AM, xi:25 = 11:25 AM

From 12:00 to 12:59, just get in "PM"

Examples: 12:10 = 12:10 PM, 12:55 = 12:55 PM

From xiii:00 to 23:59, subtract 12 Hours, make it "PM"

Examples: fourteen:55 = 2:55 PM, 23:30 = 11:thirty PM

Comparing Nautical chart

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

Case: on the hour


Example: 10 minutes past

24 Hour Clock

AM / PM

24 Hour Clock

AM / PM
00:00 12 Midnight
00:10 12:10 AM
01:00 1:00 AM 01:10 1:10 AM
02:00 2:00 AM 02:ten two:10 AM
03:00 3:00 AM 03:10 3:x AM
04:00 iv:00 AM 04:10 4:10 AM
05:00 5:00 AM 05:10 v:ten AM
06:00 6:00 AM 06:10 half-dozen:ten AM
07:00 7:00 AM 07:10 7:x AM
08:00 eight:00 AM 08:10 viii:10 AM
09:00 nine:00 AM 09:10 9:ten AM
10:00 ten:00 AM ten:10 10:10 AM
11:00 11:00 AM eleven:10 eleven:x AM
12:00 12 Apex 12:10 12:10 PM
thirteen:00 1:00 PM thirteen:10 one:10 PM
14:00 2:00 PM fourteen:ten 2:x PM
15:00 iii:00 PM 15:ten 3:x PM
sixteen:00 four:00 PM 16:10 4:ten PM
17:00 5:00 PM 17:10 five:x PM
18:00 6:00 PM 18:ten half dozen:10 PM
nineteen:00 seven:00 PM 19:ten 7:10 PM
20:00 viii:00 PM 20:x viii:ten PM
21:00 nine:00 PM 21:10 9:ten PM
22:00 10:00 PM 22:10 10:x PM
23:00 xi:00 PM 23:ten 11:10 PM

Midnight and Apex

"12 AM" and "12 PM" tin can crusade confusion, so we prefer "12 Midnight" and "12 Noon".

What Solar day is Midnight?

Midnight has another trouble: there is aught to tell united states of america "is this the beginning or ending of the day".

holiday

Imagine your friends say they are leaving for vacation at "midnight" on 12th March, what 24-hour interval should you make it to say goodbye?

Practise y'all get there on the 11th (bold 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:

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

which the railroads, airlines and war machine actually practice.

And so, when yous see something like "offer ends midnight October 15th" tell them to use one minute before or after so at that place 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 most mutual, spelling for AM is "ante meridiem" which is a Latin phrase. I recommend that spelling!

Just people sometimes utilise the phrase "ante tiptop" (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