Mathematics · Class 4 · Time · Term 3

Using a.m. and p.m.

Understand the 12-hour clock format by learning the difference between a.m. (ante meridiem) and p.m. (post meridiem) to describe time.

TL;DR:How do we know if a plan to meet a friend at '7 o'clock' means for early morning breakfast or for late evening dinner? Let's learn about two simple helpers, a.m. and p.m., that solve this problem!

• CBSE Learning Outcomes
• NCERT Class 4 Mathematics: Chapter 4 - Tick-Tick-Tick

About This Topic

This topic introduces students to the 12-hour clock convention using 'a.m.' and 'p.m.', a foundational concept in time-telling. As per the NCERT framework for Class 4, students are expected to move beyond qualitative time descriptions (like morning, evening) to a more formal and quantitative understanding. This lesson is crucial as it builds the groundwork for reading schedules, timetables, and eventually understanding the 24-hour format commonly used in India for railways and aviation. The distinction between ante meridiem (before midday) and post meridiem (after midday) helps children structure their daily routines with precision.

The pedagogical approach should be rooted in the child's own experiences. By connecting a.m. and p.m. to their daily activities like waking up, going to school, having lunch, and going to bed, the concept becomes tangible and less abstract. This topic not only enhances their mathematical skills in the domain of 'Measurement' but also imparts a critical life skill, enabling them to organise, plan, and communicate about their day effectively. It is a bridge between their intuitive sense of time and the standardised system used globally.

Key Questions

1. Explain the difference between 7:00 a.m. and 7:00 p.m. using daily activities.
2. Identify whether daily events like school assembly, lunch, and bedtime happen in the a.m. or p.m.
3. Analyse a list of times and sort them into a.m. and p.m. categories.

Learning Objectives

• Differentiate between the a.m. and p.m. periods of a day.
• Associate daily activities and routines with the correct a.m. or p.m. designation.
• Write time in the 12-hour format using the standard a.m. and p.m. notation.
• Order a series of events chronologically based on their a.m. and p.m. times.
• Solve simple word problems involving the 12-hour clock format.

Key Vocabulary

a.m. (ante meridiem)	The time period from midnight to noon.
p.m. (post meridiem)	The time period from noon to midnight.
Noon	12 o'clock in the middle of the day, also known as midday.
Midnight	12 o'clock at night; the time when one day ends and another begins.
12-hour clock	A system of telling time where the 24 hours of the day are divided into two 12-hour periods.

Watch Out for These Misconceptions

Common Misconception

Students think 12:00 a.m. is noon and 12:00 p.m. is midnight.

What to Teach Instead

Explain that 'p.m.' stands for post meridiem, meaning 'after midday'. So, 12:00 p.m. is midday (noon) itself, marking the start of the afternoon. Conversely, 12:00 a.m. is midnight, the moment a new day begins.

Common Misconception

A common error is believing a.m. is for the entire morning and p.m. is for the entire evening, forgetting the afternoon.

What to Teach Instead

Clarify that the a.m. period runs from midnight (12:00 a.m.) up to 11:59 a.m. The p.m. period starts at noon (12:00 p.m.) and covers the afternoon, evening, and night until 11:59 p.m.

Common Misconception

Students write redundant phrases like '9:00 a.m. in the morning'.

What to Teach Instead

Teach them that 'a.m.' is a shorthand for 'in the morning' (ante meridiem). Therefore, saying both is unnecessary. One should either say '9 o'clock in the morning' or simply '9:00 a.m.'.

Active Learning Ideas

Four Corners

My Daily Routine Clock

Students create a clock on a paper plate, dividing it into a.m. and p.m. halves. They then draw or write their key daily activities (like waking up, school, lunch, playtime, dinner) at the correct time and in the correct half.

40 min·Individual

Four Corners

a.m./p.m. Sorting Race

The class is divided into two teams. The teacher calls out an activity with a time, for example, 'Eating breakfast at 8:00'. A student from each team runs to the board and writes the time under the correct column: 'a.m.' or 'p.m.'.

20 min·Small Groups

Four Corners

Human Timeline

Give each student a card with a time and an activity (e.g., 7:00 a.m. - Wake up, 1:00 p.m. - Lunch, 8:00 p.m. - Dinner). Students must then arrange themselves in a line in the correct chronological order from the start of the day to the end.

15 min·Whole Class

Real-World Connections

• Reading a school timetable to know if the music class is at 11 a.m. or 3 p.m.
• Setting an alarm for 6:00 a.m. to wake up for school.
• Checking the timing for a favourite cartoon show, for instance, at 5:00 p.m.
• Understanding shop timings, like a chemist shop that is open from 9 a.m. to 10 p.m.
• Looking at a bus or train ticket to see the departure time, for example, 8:15 p.m.

Assessment Ideas

Exit Ticket

Exit Ticket: Ask students to write the current classroom time on a slip of paper with the correct a.m. or p.m. label before leaving the class.

Quick Check

Worksheet with two columns, a.m. and p.m. Students sort a mixed list of times and activities (e.g., 'sunrise', '2:00 in the afternoon', '9:30 at night') into the correct column.

Quick Check

A short quiz including questions that require students to write the time for given events (e.g., 'quarter past seven in the evening') and identify errors in given times (e.g., 'I eat lunch at 1:00 a.m.').

Frequently Asked Questions

Why is 12:30 in the afternoon called p.m. and not a.m.?

The switch from a.m. to p.m. happens exactly at 12:00 noon. So, any time after 12:00 noon, even 12:01, is considered 'post meridiem' or 'after midday', which is why we use p.m.

What do a.m. and p.m. actually mean?

They come from Latin. 'a.m.' stands for 'ante meridiem', which means 'before midday'. 'p.m.' stands for 'post meridiem', which means 'after midday'. Midday is another word for noon.

If a new day starts at midnight, why is it 12:00 a.m. and not 00:00?

That's a great question! While the 24-hour clock (used by the railways) uses 00:00, the 12-hour clock starts its cycle from 12, not 0. So, the day begins at 12:00 a.m. and goes through 1, 2, 3... up to 11.