Time runs your day. You need to know the time for everything. You have to wake up on time. You meet friends on time. You must finish your work on time. But do you truly know the simple time system you use every day?
You see the letters “AM” and “PM“ all the time. A meeting is set for 10 AM. A movie starts at 7 PM. These two small labels run the 12 hour clock system. Do you ever get mixed up? Do you wonder when the clock switches from PM back to AM?
This article makes it all crystal clear. You will learn the true start of AM and PM. You will find the easy way to always remember which one is which. You will also see why the 24 hour clock is often better for travel and big plans. You can master time today.
What AM and PM Mean Simply
Let’s get right to the basic meaning. AM and PM are short words from the old language Latin. They tell you where the sun is during the day. This is relative to the local meridian. The meridian is just an imaginary line of longitude passing over a place.
- AM means ante meridiem.
- PM means post meridiem.
The word meridiem itself means midday or noon. So we can easily translate the phrases.
Ante meridiem means before midday.
Post meridiem means after midday.
This makes the time system easy to follow. AM is the morning. It is the time before noon. PM is the afternoon and evening. It is the time after noon. The clock changes right at 12 o’clock.
The AM Time Cycle The Morning
The AM cycle starts right after the middle of the night. Midnight is the start of a new day. Think of the hours you are sleeping. Think of the hours you are eating breakfast and starting your job or school. These are AM hours.
The clock starts at 1200 AM. This is midnight. The day is brand new. Then the clock moves one hour to 1 AM. It goes 2 AM, 3 AM, and so on. It keeps going until 11 AM. After 11 AM it gets ready to switch.
Let’s look closely at the morning hours.
- 1200 AM is midnight. This is the exact moment the date changes.
- 1 AM is one hour after the date changed. It is deep night.
- 6 AM is when many people wake up.
- 11 AM is the very end of the morning hours. This is just before lunch.
You use AM for all your morning events. You wake up early at 6 AM. You start your classes at 9 AM. You eat a small snack before the day gets too busy.
The PM Time Cycle The Afternoon and Night
The PM cycle starts right at the middle of the day. Noon is the center point of your day. It is the exact moment the clock changes from morning to afternoon.
The clock starts at 1200 PM. This is noon or midday. Then the clock moves to 1 PM. This is the early afternoon. It goes 2 PM, 3 PM, and so on until 11 PM. After 11 PM it prepares to switch back to a new day.
Let’s look closely at the afternoon and night hours.
- 1200 PM is noon. This is usually lunch time.
- 1 PM is the start of the true afternoon. The sun is high.
- 5 PM is when many people finish their work day.
- 7 PM is often dinner time.
- 11 PM is the very last full hour before midnight. Most people are asleep or getting ready for bed.
You use PM for all your afternoon and night plans. You finish work at 5 PM. You watch a movie at 8 PM. You go to sleep before midnight.
The Two Tricky Times
Two times during the day make people confused. This is 1200 AM and 1200 PM. Knowing what each one means removes all doubt.
1200 PM Means Noon Midday
Remember PM means post meridiem which is after midday. But the PM cycle starts at midday.
- 1200 PM is Noon. It is the middle of the day.
Think about the minute before 1200 PM. At 1159 AM you are still ante meridiem or before midday. One minute later at 1200 the clock hits the meridian. It is now the start of the “after midday” cycle.
Always use 1200 PM for the middle of the day. If you set a time for lunch, set it for 1200 PM.
1200 AM Means Midnight New Day Start
Remember AM means ante meridiem which is before midday. The AM cycle runs from midnight up to noon.
- 1200 AM is Midnight. It is the start of the new day.
This is when the date changes. If a day changes from Friday to Saturday, it happens at 1200 AM Saturday. This is the most confusing time for people. A party set for 1200 AM on Sunday means the very first moment of Sunday morning. It does not mean late Saturday night. It is the moment Saturday becomes Sunday.
To make things very clear for travel or big plans, many people just say “noon” or “midnight” instead of using the number 12 with AM or PM. This takes away all confusion.
Read: 12 PM Nederlandse Tijd: Your Ultimate Global Time Zone Conversion Guide
Why We Use The 12 Hour Clock
You might wonder why we use a time system that repeats the numbers 1 through 12 two times each day. Wouldn’t it be easier to just count from 1 to 24?
The 12 hour clock is very old. It started thousands of years ago with the ancient Egyptians. They split the day and night into 12 parts using things like shadow clocks and water clocks. This way of telling time is deep in our culture.
The system is nice because it works well on a simple round clock. A clock uses 12 numbers in a circle. Your brain quickly sees the hands on the clock. It doesn’t have to think about a big number like 22. For your simple, daily use, it is easy and feels natural.
But the 12 hour clock has one big weakness. It must have AM or PM to be fully clear. If you just say 3 o’clock, you do not know if you mean morning or afternoon. Because of this lack of clarity, a better time system was created.
The Best Choice The 24 Hour Clock
When you need the time to be perfectly clear, you should use the 24 hour clock. This system completely removes the need for AM and PM. It counts every hour from midnight at 0000 all the way up to 2359.
People like soldiers, doctors, airplane pilots, and many large companies use the 24 hour clock. This is because it removes all chance of error. If the time is 1500, it can only mean 3 PM. If the time is 0800, it can only mean 8 AM.
How to Change From 12 Hour to 24 Hour Time
Changing between the two systems is very simple. There is one main rule to remember.
For AM Hours The Morning
The hours from 1 AM to 11 AM are easy. You just keep the number. You add a zero in front if the number is only one digit.
| 12 Hour Time | 24 Hour Time |
| 1 AM | 0100 |
| 8 AM | 0800 |
| 11 AM | 1100 |
The start of the day, midnight or 1200 AM, is also simple.
| 12 Hour Time | 24 Hour Time |
| 1200 AM (Midnight) | 0000 |
For PM Hours The Afternoon
This part needs a little bit of addition. For all PM hours except 1200 PM, you add 12 to the hour number.
| 12 Hour Time | Calculation | 24 Hour Time |
| 1 PM | $1 + 12$ | 1300 |
| 5 PM | $5 + 12$ | 1700 |
| 10 PM | $10 + 12$ | 2200 |
The moment of noon, 1200 PM, is the simplest PM conversion. You don’t add 12.
| 12 Hour Time | 24 Hour Time |
| 1200 PM (Noon) | 1200 |
When Should You Use The 24 Hour Clock?
You should use the 24 hour clock any time being wrong about the hour would cause a problem.
- Airplanes and Trains When you book a flight or train ride, use 24 hour time so you don’t miss your ride. This is very important.
- Hospital and Doctor Visits A nurse or doctor uses 24 hour time to give you medicine at the exact right hour. This keeps you safe.
- Talking to People in Other Countries When you talk to someone far away, the 24 hour format makes sure everyone knows if you mean morning or night.
- Computers and Technology All computer programs use 24 hour time by default because it is always correct and never confusing.
Using 24 hour time makes sure everyone knows the exact hour you mean. There is no question at all.
Master Your Time Now
You now have a clear understanding of AM and PM time. Knowing this difference means you will always show up on time. You will always set a clear time for your friends or family.
You know that AM is the long part of the day before noon. It runs from the start of the day until midday.
You know that PM is the long part of the day after noon. It runs from midday until the day ends.
You have learned the tricky parts. 1200 PM is noon. 1200 AM is midnight.
You also learned that the 24 hour clock is the best way to be clear. It simply counts from 0 to 23. This is the system you should use for big plans and work calls.
Take charge of your schedule. Use the right time format for the right moment. Get rid of all time confusion starting today.
Frequently Asked Questions
What does AM of PM time mean in English?
AM of PM time just means AM or PM time in English. It is the name for the 12 hour clock system. This system splits the day into two parts the AM part and the PM part.
What is the easiest way to remember AM and PM?
The easiest way is to think of the word meridiem which means noon. AM is before noon. PM is after noon.
Is 12 oclock at night AM or PM?
12 oclock at night is 1200 AM which is midnight. It is the exact moment a new day begins. The AM time is from midnight until noon.
Is 12 oclock in the afternoon AM or PM?
12 oclock in the afternoon is 1200 PM which is noon or midday. It is the exact moment the clock switches from the morning time to the afternoon time.
Why do some countries use the 24 hour clock instead of AM and PM?
They use the 24 hour clock to make sure no one is confused between AM and PM. It is always clear because every hour has its own special number from 0000 to 2359.
What is 2 PM if you use 24 hour time?
To change 2 PM to 24 hour time, you must add 12 to the number 2. So 2 PM is 1400 in the 24 hour format.
Does 12 PM mean I have 12 hours left in the day?
Yes, 12 PM noon means you have exactly half of the day left. A whole day is 24 hours. Noon is the 12 hour mark. From 12 PM to 12 AM is exactly 12 hours.
