OK, What Do 'A.M.' and 'P.M.' Actually Stand For?
Time is an integral part of everything we do. Telling time is one of the primary things that little kids learn when they head off to school. It’s critical to understand the importance of time to know when to wake up in the morning, when to head to bed at night and to be on time for all of your activities in between.
Along with telling time comes the ability to write it properly. Most people know that the morning hours of the day are referred to as a.m., while the afternoon and evening hours are designated as p.m. While these Latin terms seem to be just a standard part of giving the time of day, there is meaning behind the abbreviations. We take a look at what a.m. and p.m. stand for, how to punctuate them correctly, and how the abbreviations factor in for noon and midnight.
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What Do A.M. and P.M. Stand For?
The United States is one of several countries that uses the 12-hour clock format when telling time. That format serves as the dividing line for a.m. and p.m. hours.
A.M. Meaning
A.M. stands for "ante meridiem," which means "before midday." A.M. represents the first 12 hours of the day.
P.M. Meaning
P.M. stands for "post meridiem." It means "after midday" and refers to the last 12 hours of the day.
The letters help provide a convenient way to separate the morning, afternoon and evening hours.
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How Do You Punctuate A.M. and P.M.?
While there are several ways that are widely accepted to write the a.m. and p.m. abbreviations, the most common way is to use lowercase letters, and put periods between the letters. In fact, several official grammar guides, including the Associated Press (AP) style and Chicago Manual of Style, recommend writing it this way.
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What Is A.M. and P.M. in Military Time?
Military time may be one of the best ways to eliminate confusion when telling time. It’s often used by military personnel and emergency services, for the sake of clarity. Instead of working on the 12-hour clock format, military time works on a 24-hour time frame. The hours operate from 00 to 23, with 00 happening at midnight.
For example, with military time, 1:00 a.m. would simply be noted as 01:00. With 1:00 p.m., it would be noted as 13:00. With 11 p.m., it would be noted as 23:00.
This system eliminates the need for using a.m. and p.m. time designations.
It also eliminates confusion with 12 noon and midnight, since they are noted as 12:00 and 00:00, respectively.
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How Do Noon and Midnight Work With A.M. and P.M.?
And speaking of noon and midnight, they can be a little tricky with using a.m. and p.m. abbreviations.
At 12 noon, the sun reaches its highest level. Technically, this time is not ante meridiem or post meridiem. Many people still refer to 12 noon as "12:00 p.m.," but it actually wouldn’t receive either designation. Saying "12 noon" is more accurate.
As for midnight, that time is often referred to as "12:00 a.m." But "12 midnight" would be the more accurate way to say it.
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