What Do AM and PM Stand For? | Meaning & Examples
AM and PM stand for “ante meridiem” (before midday) and “post meridiem” (after midday). In parts of the world with a 12-hour time system, people use “a.m.” or “p.m.” to clarify which hour they’re referring to. For example, 6:30 a.m. is morning, and 6:30 p.m. is evening.
The following tips and examples will help you understand when to use a.m. and p.m. and how to format these abbreviations correctly. In most cases, you should write “a.m.” and “p.m.” with periods. The QuillBot Grammar Checker can help you do just that.
The baby shower is scheduled for 11:30 a.m. to 2:00 p.m.
There will be an intermission from 7:30 to 8 p.m.
AM and PM meaning
The meanings of a.m. and p.m. are based on Latin words that mean “before midday” and “after midday.”
AM meaning
The abbreviation “a.m.” stands for the Latin words “ante meridiem.” When a time includes “a.m.,” it occurs between midnight and noon (the first half of the day). Although most people don’t start their day at midnight (i.e., when they’re sleeping), each calendar day starts at midnight. The “a.m.” part of each calendar day ends at 11:59 a.m. (right before noon).
We have a very early flight tomorrow, so we need to wake up at 4 a.m.
Melfi stayed awake until 1:30 a.m. writing a resume and then slept until 9 a.m.
PM meaning
The abbreviation “p.m.” stands for the Latin words “post meridiem,” which means “after midday.” The hours that include “p.m.” are from noon to midnight (the second half of each calendar day). The last minute of each calendar day is 11:59 p.m. (right before midnight, when a new calendar day begins).
The concert ends at 11 p.m., so we should be home before midnight.
We need to order the pizzas by 5:30 p.m. if we want to eat dinner by 6:30.
How to write AM and PM
Unless your style guide or assignment requirements say otherwise, if you’re using US English, write “a.m.” and “p.m.” in lowercase with a period after each letter. The three most common style guides for academic writing—APA, MLA, and Chicago—all prefer lowercase letters and periods in addition to the following:
- Use the cardinal number (without “:00”) for a time that falls at the top of the hour (e.g., “11 p.m.”).
- Otherwise, separate the hour and minutes with a colon (e.g., “7:30 a.m.”).
- When writing a time range, if both times are a.m. or p.m., you only need to write “a.m.” or “p.m.” at the end of the time range (e.g., “The morning session is from 8 to 9:30 a.m.”).
We were at the cinema from 11:30 a.m. to 2:45 p.m.
Frequently asked questions about am and pm
- Should AM and PM be capitalized?
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AM and PM should usually not be capitalized, but different style guides have different requirements. Unless your style guide says otherwise, “a.m.” and “p.m.” should be lowercase with a period after each letter (e.g., “I’m serving dinner at 7:30 p.m.”).
When writing “a.m.” and “p.m.” in lowercase, the QuillBot Grammar Checker can help you remember where to use a period.
- What is the difference between AM and PM?
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The difference between AM and PM is that “a.m.” refers to the hours from noon to midnight, and “p.m.” refers to the hours from midnight to noon.
For example, 12:01 a.m. is the minute after midnight, and 11:59 a.m. is the minute before noon. Use the abbreviation “a.m.” after the first 12 hours of each calendar day. Use the abbreviation “p.m.” after the hours in the second half of each day.
The abbreviations “a.m.” and “p.m.” are usually written in lowercase with periods. QuillBot’s free Grammar Checker can help you format expressions of time correctly in your writing.
- Is 12 pm noon?
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Yes, conventionally 12 p.m. is noon, and 12 a.m. is midnight.
You can say “12 p.m. noon” (or just “12 noon”) and “12 a.m. midnight” (or just “12 midnight”) for clarity when making arrangements.
12 noon is the point at which morning ends and afternoon starts.
Bear in mind that the context sometimes determines what time is morning (e.g., 3 a.m may be considered morning for someone starting an early work shift but nighttime for someone who went to bed at 11:30 p.m. and has been woken up by a noisy neighbor).
QuillBot’s free Paraphraser tool can help you find alternative words and phrases for times and parts of the day such as “noon” and “nighttime.”
- Is 12 am midnight?
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Yes, conventionally, 12 a.m. is midnight, and 12 p.m. is noon/midday.
You can say, “12 a.m. midnight” (or just “12 midnight”) and “12 p.m. noon” (or just “12 noon”) for clarity when making arrangements.
QuillBot’s free Paraphraser tool can help you find alternative words and phrases for time expressions like “midnight” and “noon.”
