AM vs. PM — What's the Difference?
By Tayyaba Rehman — Updated on September 23, 2023
AM stands for "Ante Meridiem," which is Latin for "before midday," and refers to the time period from midnight to just before noon. PM stands for "Post Meridiem," meaning "after midday," and covers the time from noon to just before midnight.
Difference Between AM and PM
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Key Differences
AM and PM are abbreviations used to specify the time of day in a 12-hour clock system. AM, standing for "Ante Meridiem," is used for the time period starting from 12:00 midnight up to 11:59 in the morning. PM, or "Post Meridiem," starts from 12:00 noon and goes up to 11:59 at night. Each term helps to clearly distinguish between the two halves of the day.
The use of AM and PM is prevalent in countries that follow the 12-hour clock system as opposed to the 24-hour clock system. In the 24-hour system, the use of AM and PM is not necessary since each hour of the day is uniquely identified. For example, 15:00 in a 24-hour clock is equivalent to 3:00 PM in a 12-hour clock.
The abbreviations AM and PM come from Latin. AM stands for "Ante Meridiem," translating to "before midday," while PM stands for "Post Meridiem," which means "after midday." These terms have been used for centuries to standardize time-keeping and avoid ambiguity in daily schedules and activities.
It's important to note that the use of AM and PM begins anew each day at midnight and noon, respectively. When scheduling or noting time, it's crucial to specify AM or PM to ensure there's no confusion about which half of the day you are referring to. For instance, an appointment at 10:00 AM is different from one at 10:00 PM, not just in time but often in context as well.
Comparison Chart
Meaning
Ante Meridiem
Post Meridiem
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Translation
Before midday
After midday
Time Period Covered
Midnight to before noon
Noon to before midnight
Clock System
12-hour
12-hour
Usage Context
Morning hours
Afternoon and evening hours
Compare with Definitions
Am
An abbreviation for "Ante Meridiem."
The store opens at 9:00 AM.
Pm
An abbreviation for "Post Meridiem."
The movie starts at 8:00 PM.
Am
Used in the 12-hour clock system.
I usually wake up at 6:00 AM.
Pm
Used in the 12-hour clock system.
The event ends at 5:00 PM.
Am
Refers to the time period from midnight to before noon.
The flight leaves at 10:30 AM.
Pm
Refers to the time period from noon to before midnight.
Dinner is served at 7:00 PM.
Am
Commonly used to schedule morning activities.
The meeting is scheduled for 11:00 AM.
Pm
Commonly used to schedule afternoon and evening activities.
The concert is at 9:00 PM.
Am
Latin for "before midday."
AM signifies the first half of the day.
Pm
Latin for "after midday."
PM denotes the second half of the day.
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.
Common Curiosities
What does AM stand for?
AM stands for "Ante Meridiem," which is Latin for "before midday."
When does PM start and end?
PM starts at noon and ends just before midnight.
What does PM stand for?
PM stands for "Post Meridiem," meaning "after midday" in Latin.
Is AM used for morning or evening?
AM is used to denote the morning hours.
Can 12:00 be AM or PM?
12:00 at night is considered AM, and 12:00 in the daytime is considered PM.
When does AM start and end?
AM starts at midnight and ends just before noon.
Are AM and PM used worldwide?
AM and PM are mostly used in countries that follow the 12-hour clock system.
What comes after 11:59 PM?
After 11:59 PM, it becomes 12:00 AM.
Is PM used for morning or evening?
PM is used to denote the afternoon and evening hours.
Are AM and PM used in the military?
The military typically uses a 24-hour clock, making AM and PM unnecessary.
What comes after 11:59 AM?
After 11:59 AM, it becomes 12:00 PM.
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Written by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
