| From 12:01 pm to 12:59 pm, do nothing | The main weakness of the 12-hour system is a widespread confusion about which abbreviation should be used for noon and midnight: neither moment can logically be identified as before noon am or after noon pm |
|---|---|
| From 12:00 to 12:59, just add pm after the time | To avoid any confusion when referring to the precise moment of noon or midnight, we recommend using the designations 12 noon and 12 midnight instead |
| The Egyptians are thought to be responsible for dividing the day into 24 equal parts | 12-hour clock at noon: 12 am or 12 pm? From 13:00 to 0:00, subtract 12 hours and use pm |
|---|---|
| One way to overcome this problem is to sacrifice accuracy for clarity | From 1:00 pm to midnight, add 12 hours |
Your friend could ask you to be at the airport at 12:01 am on April 13 or, if the following midnight is meant, at 11:59 pm on April 13.
| com, designate midnight as 12 am and noon as 12 pm | One account suggests that this custom evolved because the Egyptians commonly used the base 12, counting the 3 joints in their fingers, not including the thumb |
|---|---|
| Imagine being asked to pick up a friend at the airport at 12:00 am on April 13 |
The abbreviations am and pm derive from Latin:• Alternatively, the 24-hour format could be used.
10