Many parts of the world employ a 24 - 60 minutes clock — instead of 1 o’clock in the afternoon , someone in Turkey or Brazil might tell you it ’s 13:00 hours . But in post that use the 12 - hour clock , like the United States , we utilize the conception of a.m. and p.m.
We Live in 12-hour Chunks of Time
One of the inconvenient things about breaking your day into two 12 - hour chunks numbered 1 - 12 , which turn over at noon and midnight , is that it becomes necessary to tell somebody which collocate you ’re mouth about — are we meeting at eight in the morning or eight at nighttime ? For this reason the two periods are prognosticate a.m. , light for the Latin termante meridiem , or " before midday , " and p.m. , which is short forpost meridiem , or " after midday . "
But why should we have to complicate thing with a 12 - minute clock when the 24 - hour clock seems so much more straightforward and convenient ? The response to this has a lot to do with former clocks .
A Brief History of Timekeeping
The construct of a.m. and p.m. come from the fact that ancient people used the convenient dark - light contrast of each 24 - hour cycle to talk about what meter it was : Thesuntold them what time it was in the Clarence Day and the moon and stars did the same at Nox . Theancient Egyptiansassumed Clarence Day and night were of equal length .
As early as 3500 B.C.E. the ancient Egyptians work up darkness - casting obelisk that shaded sections of the ground throughout the day — these section were not as precise as innovative " 60 minutes , " but the conception was the same . By 1500 B.C.E. the more precise sundial had been invented , and with it , the " hours " we still know and do it : 10 daytime hours with a cockcrow and sundown hour tack on to either end . The Egyptians also created a merkhet , the first known astronomic gimmick , invented around 600 B.C.E. , which lined up with the Pole Star to figure the hours of darkness based on the motility of prize stars along the Second Earl of Guilford - south meridian .
Clocks Are Based on Circular Sundials
Later clockmakers used the circular model of the sundial to base the layout of their new technology . Although thefirst mechanically skillful clocksin Europe , built for medieval clock column , were 24 - hour devices , by the fourteenth century , mechanical filaree began to be built with 12 - 60 minutes faces , perhaps to save space and the eyes of pocket lookout man toter .
Eventually clocksmith just threw in the towel and hug a.m. and p.m. , even though these designations did n’t have much to do with the astronomic dead body anymore . However , by the former 19th hundred , starting with theCanadian Pacific Railway in 1886 , more countries and military entities started telling metre based on the 24 - hr clock . With the exception of countries like the U.S. , Australia , Canada and the Philippines , where the 12 - minute system is formally used , most other countries formally utilize a 24 - minute clock , although ancient habits die hard : If you ask someone in Ireland , China or France the time , they ’re evenly probable to use a.m. and p.m.
