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Is it a.m. or p.m.?

Hello! This week on Ask a Teacher, we will answer a question from Max in China about the difference between a.m. and p.m.

Question:

Dear VOA teachers,

This is Max from China. During a listening exam I heard a saying like this, "The incident happened on the 400 block of Rutland Road just after 12:30 PM," and it was described as midnight. I'm confused. I think that 12:30 PM should be at noon during the day, and if I want to say the time of midnight I think AM is correct. Which one is right? Thank you for helping¹ me solve this problem.

Best regards,

Max

Answer:

Dear Max,

Thank you for writing to us.

You are correct! In the United States, we do not use a 24-hour clock in day-to-day speech. But some special fields that demand very clear communication use a 24-hour clock. So, you might hear a person describe such time as "military time." A 24-hour clock is more commonly used internationally than it is in America.

We use a 12-hour clock and abbreviations³ from Latin⁴ to tell time, a.m. (ante meridiem, meaning before midday) and p.m. (post meridiem, meaning after midday).

Our morning clock starts at 12:00 a.m. That is 0:00 (zero hundred hours), or midnight, internationally.

Morning, or a.m. hours, go until 12:00 p.m., which would also be 12:00 on an international, 24-hour clock.

But most of the time, we do not show a difference between the two forms of timekeeping in everyday speech. For example, we know that, if a friend wants to meet at 2:00 local time, hopefully they do not want to meet at 2:00 in the morning.

Let us look at a few examples to compare times.

My supervisor⁵ planned the meeting for 3 p.m.

This means that the meeting will take place at 3:00 in the afternoon.

That new superhero movie is so long; it lasted until 1 a.m.

This means that the movie did not finish until 1:00 in the morning (after midnight).

I have an evening class from 4:30 p.m. until 7:00 p.m.

This example means that the class continued from the afternoon into the evening.

Now, consider a clock for comparison⁶.

If you are reading online, we have a clock to help us understand the differences between the 24-hour clock and the 12-hour clock.

The clock is at 10:10. If it is the morning we would say it as 10:10 a.m. This would be the same internationally.

But, if it were before midnight, we would read it as 10:10 p.m. or 22:10 on a 24-hour clock.

A fun way to remember a.m. and p.m. is to listen to the song AM to PM by singer Christina Milian.

The lyrics⁷ go:

"Somebody hit the lights, so we can rock it day and night

People gettin' down, that's right, from AM to PM"

In the song, the party is starting in the early hours of the morning (after midnight) in the a.m.

And the party is so long that it goes into the afternoon, or the p.m. hours.

Please let us know if these examples and explanations have helped you, Max!

What question do you have about American English? Send us an email at [email protected]

And that's Ask a Teacher.

Words in This Story

confused – adj. to be uncertain or unable to understand something

abbreviation² – n. a shortened form of a word or name that is used in place of the full word or name