AM vs. PM: What's the Difference?
Edited by Aimie Carlson || By Janet White || Published on February 3, 2024
AM (Ante Meridiem) refers to the time from midnight to noon, while PM (Post Meridiem) denotes the time from noon to midnight.
Key Differences
AM, an abbreviation for the Latin term 'Ante Meridiem', is used to denote the time period from midnight (00:00) to just before noon (11:59). It indicates the first half of the day in the 12-hour clock system. In contrast, PM, short for 'Post Meridiem', signifies the time from noon (12:00) to just before midnight (23:59). It covers the second half of the day in the 12-hour clock format.
When using AM, time is usually understood to be during the morning or the early part of the day. For instance, 8:00 AM indicates eight o'clock in the morning. On the other hand, PM is associated with the afternoon and evening hours. For example, 3:00 PM refers to three o'clock in the afternoon.
In contexts where clarity is essential, such as travel or scheduling, AM is crucial for indicating early day activities or appointments. A flight at 9:00 AM, for instance, is scheduled for the morning. Whereas PM is essential for distinguishing activities scheduled for later in the day, like a meeting at 5:00 PM, which is understood to be in the evening.
AM times are often associated with routine morning activities like breakfast or commuting to work. It’s used in everyday language to plan events that occur before noon. Conversely, PM times are linked with afternoon and evening activities such as lunch, dinner, or evening entertainment, marking events scheduled post-noon.
In digital devices and international contexts, using AM and PM helps differentiate between morning and evening times in the 12-hour clock system, avoiding confusion with the 24-hour clock. For example, 7:00 AM in a 12-hour format is 07:00 in a 24-hour format, while 7:00 PM is 19:00.
ADVERTISEMENT
Comparison Chart
Meaning
Ante Meridiem (before noon)
Post Meridiem (after noon)
Time Range
Midnight (00:00) to just before noon (11:59)
Noon (12:00) to just before midnight (23:59)
Typical Associations
Morning activities, breakfast time
Afternoon and evening activities, dinner time
Usage Example
"The flight departs at 10:00 AM."
"The movie starts at 8:00 PM."
Clock Format
First half of the 12-hour clock
Second half of the 12-hour clock
ADVERTISEMENT
AM and PM Definitions
AM
Morning Hours.
He jogs at 6:00 AM daily.
PM
Afternoon Hours.
She has lunch at 12:30 PM.
AM
Before Noon.
The seminar starts at 11:00 AM.
PM
Evening Time.
Dinner reservations are at 7:00 PM.
AM
Early Part of the Day.
Breakfast is served at 7:00 AM.
PM
Late Day Activities.
Gym classes start at 6:00 PM.
AM
Beginning of Business Hours.
The store opens at 9:00 AM.
PM
After Noon.
The meeting is scheduled for 1:00 PM.
AM
Sunrise Period.
Sunrise today is at 5:30 AM.
PM
Sunset Hours.
Sunset is expected at 8:00 PM.
AM
First person singular present indicative of be.
PM
Alternative form of p.m.
AM
Inflection of be
PM
An examination and dissection of a dead body to determine cause of death or the changes produced by disease
AM
The first person singular of the verb be, in the indicative mode, present tense. See Be.
God said unto Moses, I am that am.
PM
A soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium
AM
A radioactive transuranic metallic element; discovered by bombarding uranium with helium atoms
PM
The person who holds the position of head of state in England
AM
A master's degree in arts and sciences
PM
Modulation of the phase of the carrier wave
AM
Modulation of the amplitude of the (radio) carrier wave
PM
After noon
PM
Between noon and midnight;
Let's meet at 8 P.M.
FAQs
Does PM include the evening?
Yes, PM includes the afternoon and evening until midnight.
What do AM and PM stand for?
AM stands for Ante Meridiem, and PM stands for Post Meridiem.
What time does AM start and end?
AM starts at midnight (00:00) and ends just before noon (11:59).
Is 12 PM noon or midnight?
12 PM is noon.
Can AM and PM be used in a 24-hour clock?
No, AM and PM are specific to the 12-hour clock format.
Is midnight referred to as 12 AM or 12 PM?
Midnight is referred to as 12 AM.
Can AM and PM be lowercased?
They can be, but capitalization is standard.
Do all countries use AM and PM?
Not all; some prefer the 24-hour clock format.
What is 3:00 PM in a 24-hour format?
3:00 PM is 15:00 in a 24-hour format.
How do I know if a time is AM or PM?
The time of day (morning or evening) indicates AM or PM.
Is 12 AM noon or midnight?
12 AM is midnight.
Is the noon hour expressed as 12 PM?
Yes, noon is expressed as 12 PM.
What happens to AM/PM in daylight saving time?
AM and PM times shift accordingly with daylight saving changes.
Is 11:59 PM followed by 12:00 AM?
Yes, 11:59 PM is followed by 12:00 AM.
Is there a space between the time and AM/PM?
Typically, a space is used (e.g., 9:00 AM).
Are AM and PM used in formal writing?
Yes, they are used in both formal and informal contexts.
How do airlines handle AM and PM in flight schedules?
Airlines use AM and PM to indicate departure and arrival times.
Can AM and PM be confusing in time zones?
Yes, especially when communicating across different time zones.
Are AM and PM capitalized?
Yes, AM and PM are usually capitalized.
What is the correct way to write AM and PM?
With periods (A.M., P.M.) or without (AM, PM).
About Author
Written by
Janet WhiteJanet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie CarlsonAimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.
