Understanding AM and PM
A standard analogue clock, and any 12-hour digital clock, only shows the numbers 1 through 12. That means every hour appears twice in a single day — once in the morning and once in the evening. AM and PM are the labels we use to tell these two versions of each hour apart. Without them, “meet me at 7:00” could mean breakfast or dinner.
Where the terms come from
AM stands for ante meridiem, a Latin phrase meaning “before midday”. PM stands for post meridiem, meaning “after midday”. Together, they split the 24-hour day into two 12-hour halves, centred on midday (noon). The word meridiem refers to the middle of the day, which is the point the whole system is built around.
The dividing lines
AM covers the period from midnight (12:00 AM) up to, but not including, midday — this is the early hours and the morning. PM covers the period from midday (12:00 PM) up to, but not including, midnight — this is the afternoon, evening and night. Each half lasts exactly twelve hours.
| Time of day | Typical times | Label |
|---|---|---|
| Night (after midnight) | 12:00 AM – 5:59 AM | AM |
| Morning | 6:00 AM – 11:59 AM | AM |
| Afternoon | 12:00 PM – 5:59 PM | PM |
| Evening and night | 6:00 PM – 11:59 PM | PM |
The two trickiest times: 12 AM and 12 PM
Midnight and midday are the two points where people most often get confused. A 12-hour clock counts 12, 1, 2, 3 … 11 and then starts again, so the hour “12” comes at the start of each half of the day, not the end. That is why it feels backwards at first.
12:00 AM is midnight — the very start of a new day. 12:00 PM is midday (noon) — the middle of the day. A simple way to remember this: right after 12:00 AM, the clock counts up through the AM hours (1 AM, 2 AM…) toward midday. Right after 12:00 PM, it counts up through the PM hours (1 PM, 2 PM…) toward midnight again.
Because 12 AM and 12 PM are so easy to mix up, many people simply write “midnight” or “noon” on invitations and timetables. It is clearer for everyone, especially children who are still learning.
Worked examples
Example 1: 7:00. At 7:00 in the morning, while most people are having breakfast, the time is written 7:00 AM. At 7:00 in the evening, while most people are having dinner, it is written 7:00 PM. The hands on an analogue clock look identical at both times; only the AM/PM label, or context such as daylight, tells you which one it is.
Example 2: half past three. If school ends at half past three in the afternoon, that is 3:30 PM. If someone is awake at half past three in the middle of the night, that is 3:30 AM.
Example 3: quarter to twelve. A quarter to twelve at night is 11:45 PM, the last quarter hour before the new day begins. Fifteen minutes later the clock reads 12:00 AM, and the AM hours start again.
AM and PM compared with the 24-hour clock
Some clocks, timetables and devices use the 24-hour clock, which counts from 00:00 to 23:59 and needs no AM or PM. Converting between the two systems follows a simple rule:
- AM hours stay the same (9:00 AM is 09:00), except that 12:00 AM becomes 00:00.
- PM hours add 12 (3:00 PM is 15:00), except that 12:00 PM stays 12:00.
| 12-hour time | 24-hour time |
|---|---|
| 12:00 AM (midnight) | 00:00 |
| 1:00 AM | 01:00 |
| 6:00 AM | 06:00 |
| 11:00 AM | 11:00 |
| 12:00 PM (noon) | 12:00 |
| 1:00 PM | 13:00 |
| 6:00 PM | 18:00 |
| 11:00 PM | 23:00 |
Common mistakes
- Thinking 12 AM is noon. It is midnight. Noon is 12 PM.
- Thinking the day starts at 1 AM. A new day begins at 12:00 AM, one hour before 1:00 AM.
- Reading the clock hands and forgetting the label. The hands alone can’t tell you whether it is morning or evening, so always look for the AM/PM label or think about the time of day.
- Getting the order wrong. AM always comes before PM within the same calendar day, so 11:59 AM is followed by 12:00 PM.
Tips for remembering
- AM is for After midnight, and the morning. PM is for the Past-midday hours, the afternoon and evening.
- Link the hour to what you are doing: waking up and breakfast are AM, while dinner and bedtime are PM.
- Remember that both AM and PM begin with 12, not with 1.
Try it yourself
Work out each answer, then check it below.
- School starts at 8:15 in the morning. How do you write this time?
- Which is later: 11:30 AM or 12:30 PM?
- Is 12:00 AM midnight or noon?
- What is 4:00 PM on the 24-hour clock?
- What is 21:00 on the 12-hour clock?
Answers: (1) 8:15 AM. (2) 12:30 PM is later, by one hour. (3) Midnight. (4) 16:00. (5) 9:00 PM.
Frequently asked questions
Is noon 12 AM or 12 PM?
Noon is 12:00 PM. Midnight is 12:00 AM.
Does 12:30 AM come before or after midnight?
After. It is thirty minutes into the new day, in the small hours of the morning.
Do I have to use capital letters?
No. AM, PM, am, pm, a.m. and p.m. all mean the same thing. What matters is using one style consistently.
Why don’t all clocks show AM and PM?
An analogue clock only has twelve numbers, so it can’t show which half of the day it is. Many digital clocks add an AM/PM label, and others use the 24-hour system instead.
Practise it with TimeTutor
TimeTutor’s lessons include a “Morning / Afternoon / Evening / Night” indicator beside every clock, helping learners build an intuitive sense of which times fall into AM and which into PM. You can also read our guide to analogue vs digital time to see how the two ways of showing time connect.
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