Lowercase a.m. and p.m. and always use periods. Lowercase noon and midnight. Do not use 12 noon or 12 midnight (redundant). Use noon or midnight.
According to all of the major style guides, a.m. and p.m. should be lowercased and the letters should be separated by periods when used in sentences. Style guides also recommend separating the time numeral from the abbreviation with a space.
Punctuation of AM and PM
It would be unusual to punctuate these terms when using standard capital letters, though. Finally, keep in mind that you do not need an extra period after the abbreviation when punctuating a time like this at the end of a sentence.
Yup, the abbreviation a.m. is short for the Latin ante meridiem, meaning “before noon,” which refers to the period from midnight until noon. And, p.m. then? It's short for the Latin phrase post merīdiem meaning “after noon.” Got it. One minute after noon is 12:01 p.m.
Time: lowercase a.m. and p.m. with periods and always figures proceeding. The exception is at the hour, you do not include “:00.” If it is a time range, use only a.m. or p.m. once within the same time of day (e.g. 8-9 a.m.). Use both a.m. and p.m if it is not the same time of day (e.g., 9:30 p.m.- 1 a.m.).
Lowercase a.m. and p.m. and always use periods. Lowercase noon and midnight. Do not use 12 noon or 12 midnight (redundant).
In addition, when writing the times 1:00 pm, 2:00 pm, etc., it is perfectly acceptable to omit the zeroes and write 1 pm, 2 pm, instead. Finally, note that while in the US we use a 12-hour clock, some countries use a 24-hour clock, or military time.
There are six ways to write the abbreviations for ante meridiem (before noon) and post meridiem (after noon): All caps with periods: 10 A.M., 10 P.M. Small caps with periods: 10 A.
If somebody ask you the time, I guess you aren't going to say at 9 pm. Your answer will be it's 9pm.
There are a few generally accepted ways to write these abbreviations in your writing. The first and most common way to write them is with lowercase “a.m.” and “p.m.” This way requires periods, and both Chicago Style and AP Style recommend this way of writing the abbreviations.
Occasionally computer programs encourage you to write “AM” and “PM” without a space before them, but others will misread your data if you omit the space. The nonstandard habit of omitting the space is spreading rapidly, and should be avoided in formal writing.
If the time phrase comes before an independent clause or sentence, use a comma after the time phrase. If the time phrase comes after an independent clause or sentence, no comma is necessary.
ALL CAPS, small caps, or lower case (e.g., 12 AM, 12 AM, or 12 am) With or without periods between the letters (e.g., 8 PM or 8 P.M.) With or without a space after the number (e.g., 1 AM or 1AM)
If you put a period after each letter, that's a total of four characters. When writing a single-digit hour such as 9:00 a.m., that's the same number of characters as the time itself and is too much real estate for the task at hand. Granted, it is true that including the periods takes away all doubt as to the purpose.
6am, 6 am, 6 AM, 6 a.m., 6 A.M., 6 o'clock, 06:00, or six o'clock are all correct. Personally I use 06:00 or 6am usually. It's a stylistic choice. The most grammatically correct is using "a.m." but in both business and casual written exchanges I've seen all of the above used.
When most people say 12pm, typically they're talking about the middle of the day: 12 noon. When they say 12am, they normally mean 12 midnight. While most people follow this convention, technically it's not quite right – as you'll see from the definition of am and pm below.
12am and 12pm are both incorrect. Neither should be used. You should really pay attention to the abbreviation. "a.m." means "ante meridiem" which means "before midday" and p.m. means "post meridiem", which means "after midday".
Another convention sometimes used is that, since 12 noon is by definition neither ante meridiem (before noon) nor post meridiem (after noon), then 12am refers to midnight at the start of the specified day (00:00) and 12pm to midnight at the end of that day (24:00).
A comma should follow the time range if the sentence continues: “The meeting is scheduled for August 31, 7-9 p.m., and will feature a guest speaker.” A reference to day, date, and time requires commas between each pair of elements: “The meeting is scheduled for Wednesday, August 31, 7-9 p.m.” (And don't precede a time ...
In the evening introduces the sentence and needs to be set off with a comma. You also need a comma after a dependent clause, as in the second example.
Common starter words for introductory clauses that should be followed by a comma include after, although, as, because, if, since, when, while.
The abbreviations a.m. and p.m. stand for the Latin ante meridiem and post meridiem, meaning before and after midday. These abbreviations should be used only with numerals ( e.g. 9:00 a.m. or 9 a.m. , not nine a.m. ).