A.M., P.M., and Daily Schedules - Second Grade Mathematics
A single day on planet Earth contains exactly 24 hours, but most analog and digital clocks only display numbers from 1 to 12. Because the clock numbers repeat twice every single day, we need a way to distinguish between 8 o'clock in the morning when you eat breakfast and 8 o'clock at night when you get ready for bed! To solve this mystery, time is divided into two 12-hour halves labeled A.M. and P.M. In this chapter, you will master the definitions and Latin origins of A.M. and P.M., learn the midnight and noon transition points, and organize daily activities into realistic schedules.
The 24-Hour Day Divided into Two Halves
Earth makes one full rotation on its axis every 24 hours. A standard clock face only has 12 numbers, so the hour hand must travel around the clock face twice every day.
The 24-Hour Cycle:
+-----------------------------------+-----------------------------------+
| A.M. | P.M. |
| (Morning / 12 Hours) | (Afternoon & Night / 12 Hours)|
+-----------------------------------+-----------------------------------+
12:00 Midnight to 11:59 Morning 12:00 Noon to 11:59 Night
What Does A.M. Mean?
A.M. stands for the Latin phrase Ante Meridiem, which translates into English as "before midday" or "before noon." A.M. begins at the stroke of 12:00 Midnight (when most people are sound asleep) and continues through the sunrise, breakfast, and morning school hours, ending at 11:59 in the morning just before lunchtime.
What Does P.M. Mean?
P.M. stands for the Latin phrase Post Meridiem, which translates into English as "after midday" or "after noon." P.M. begins at 12:00 Noon (lunchtime) and continues through afternoon recess, homework time, dinner, and bedtime, ending at 11:59 at night just before midnight.
The Great Boundary Benchmarks: Midnight and Noon
The two transition points between A.M. and P.M. occur at the 12s: Midnight and Noon.
The Two 12 O'Clocks:
12:00 MIDNIGHT: Exactly 12:00 A.M.
(Middle of the night, dark outside, begins a brand-new day!)
12:00 NOON: Exactly 12:00 P.M.
(Middle of the day, sun high in the sky, lunchtime!)
The Switch That Flips
At 11:59 A.M., you are in the morning. One minute later, at 12:00 Noon, the label instantly flips to P.M.! At 11:59 P.M., you are at late night. One minute later, at 12:00 Midnight, the label flips to A.M., and a brand-new calendar date begins!
Mapping Daily Schedules to A.M. and P.M.
Understanding A.M. and P.M. allows you to build realistic schedules of daily life.
A Typical Second-Grader's Daily Schedule:
Time: A.M. or P.M.? Activity:
07:00 A.M. A.M. Waking up and eating breakfast
08:30 A.M. A.M. Arriving at school / Morning math
10:15 A.M. A.M. Morning recess
12:00 P.M. P.M. Lunch in the cafeteria (Noon!)
03:15 P.M. P.M. Dismissal from school / Riding bus
05:30 P.M. P.M. Playing outside or soccer practice
06:30 P.M. P.M. Eating dinner with family
08:00 P.M. P.M. Reading a bedtime story
08:30 P.M. P.M. Falling asleep
Choosing A.M. or P.M. in Real Scenarios
When a question asks whether an event occurs at A.M. or P.M., visualize the scene: Seeing stars and eating dinner? That is P.M.! Eating pancakes while the sun rises? That is A.M.! Going to an afternoon movie at 2:00? That is 2:00 P.M.! (2:00 A.M. is the middle of the night when you are asleep!).
Practice Exercises
Exercise 1: State what the abbreviations A.M. and P.M. stand for in Latin, and provide their English meanings.
Exercise 2: Determine whether each activity takes place at A.M. or P.M.: a) Eating breakfast at 7:30, b) Eating lunch at 12:15, c) Looking at constellations in the dark night sky at 9:00, and d) Walking into your classroom to start the school day at 8:15.
Exercise 3: Is 12:00 midnight classified as A.M. or P.M.? Is 12:00 noon classified as A.M. or P.M.?
Exercise 4: A student says: "I went swimming in the outdoor community pool on a warm sunny afternoon at 3:00 A.M." Explain why the student used the wrong time label and state the correct time.
Solutions and Explanations
Solution to Exercise 1: A.M. stands for Ante Meridiem, meaning "before midday" (before noon). P.M. stands for Post Meridiem, meaning "after midday" (after noon).
Solution to Exercise 2: a) Eating breakfast at 7:30 is 7:30 A.M. b) Eating lunch at 12:15 is 12:15 P.M. c) Looking at constellations in the dark night sky at 9:00 is 9:00 P.M. d) Walking into the classroom at 8:15 is 8:15 A.M.
Solution to Exercise 3: 12:00 midnight is classified as 12:00 A.M. (the start of the morning half of the day). 12:00 noon is classified as 12:00 P.M. (the start of the afternoon/evening half of the day).
Solution to Exercise 4: The student used 3:00 A.M., which represents three o'clock in the middle of the night when it is completely dark outside and most people are asleep in bed. A warm, sunny afternoon activity takes place after noon, so the student should have used P.M.: 3:00 P.M.