Each time comes round twice
The short hand of a clock takes 12 hours to go once around the face. A day is 24 hours long, so the short hand goes around twice every day, and every time on the face happens twice.
At 7 in the morning, when you might be getting up, the clock shows 7:00. At 7 in the evening, around dinner time, it shows 7:00 again, and the face looks exactly the same.
This face shows 7:00. It looks the same at 7 in the morning and at 7 in the evening.
The first lap is am
To tell the two apart, the day is split into two laps of 12 hours. The first lap starts at midnight, in the middle of the night, and runs until noon, the middle of the day.
Every time in the first lap has am written after it. So 7:00 in the morning is written 7:00 am.
The top row is the first lap, from midnight to noon. The mark is at 7:00 am.
The second lap is pm
The second lap starts at noon and runs until midnight. Every time in the second lap has pm written after it. So 7:00 in the evening is written 7:00 pm.
7:00 pm sits in the same place in the second lap as 7:00 am does in the first. It is the same clock time, 12 hours later.
7:00 pm is in the second row, directly below 7:00 am.
Noon and midnight
Noon and midnight are the two places where one lap hands over to the next. Noon starts the second lap, so noon is 12:00 pm. Midnight starts the first lap, so midnight is 12:00 am.
One minute after noon it is 12:01 pm, and the second lap carries on through 1:00 pm, 2:00 pm and so on, up to 11:59 pm. The next minute is midnight, 12:00 am, and a new day begins with the first lap.
This is the pair that is easiest to mix up: 12:00 pm is lunchtime, and 12:00 am is the middle of the night.
The mark is at noon, the start of the second lap: 12:00 pm.
11:00 am = 11 o'clock: the long hand is on 12 and the short hand points straight at 11
Set the clock to 12:00 pm
Turn the long hand from 11:00 am on past 12. At noon the time moves into the second half of the day, and am becomes pm.
The mark is at midnight, the start of the first lap and of the day: 12:00 am.
Before noon or after noon
To choose between am and pm, ask whether the time comes before noon or after it. Breakfast at 8 in the morning is before noon, so it is 8:00 am. Dinner at 6 in the evening is after noon, so it is 6:00 pm.
The letters come from Latin: am means before midday, and pm means after midday. A time written without them, such as 8:00, could be either of two moments in the day, so the am or pm is part of the time.