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CBSE Class 3 Mathematics★ 5–6 marks · CBSE Class 3 Mathematics (Math-Magic) Chapter 7

Time Goes On

Reading the clock — hour, half-hour, quarter. AM and PM. Calendar — days, weeks, months. Age calculation and sequencing events. CBSE Class 3 Mathematics (Math-Magic) Chapter 7.

⏱ 10 min readEasy difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Read an analog clock: o'clock (long hand at 12), half past (long hand at 6), quarter past (long hand at 3), quarter to (long hand at 9)
2Understand AM (midnight to noon) and PM (noon to midnight) — and when to use each
3Read a calendar: identify today's date, day of the week, month, and year
4Calculate the number of days between two dates; determine what day a future/past date falls on
5Calculate age from birth year; sequence events in chronological order (earliest to latest)

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Why this chapter matters

Time is the most practical math skill — children use it every day to know when to wake up, eat, go to school, and sleep. This chapter teaches clock reading (o'clock, half past, quarter past/to), AM/PM, and calendar skills (days, weeks, months). It also introduces age calculation and event sequencing (before/after, earlier/later). Mastering time builds independence and responsibility.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

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Class 2 Mathematics: Time (basic)

Must know days of the week, months of the year, and basic clock reading (o'clock only).

Time Goes On

Reading the Clock

A clock has TWO hands:

Short hand: Shows the HOUR
Long hand: Shows the MINUTES

The Numbers on a Clock

The clock has numbers 1 to 12. As time passes, the hands MOVE.

O'Clock (Exact Hour)

When the LONG hand is at 12 and the SHORT hand is at a number, it is that number O'CLOCK.

8:00 — Eight o'clock (Short hand at 8, long hand at 12)
3:00 — Three o'clock (Short hand at 3, long hand at 12)
12:00 — Twelve o'clock (Both hands at 12)

Half Past

When the LONG hand is at 6 and the SHORT hand is HALFWAY between two numbers, it is HALF PAST the first number.

8:30 — Half past eight (Long hand at 6, short hand between 8 and 9)
3:30 — Half past three (Long hand at 6, short hand between 3 and 4)

Remember: Half past means 30 minutes have passed.

Quarter Past

When the LONG hand is at 3, it is QUARTER PAST the hour.

8:15 — Quarter past eight
3:15 — Quarter past three

Remember: Quarter past means 15 minutes have passed.

Quarter To

When the LONG hand is at 9, it is QUARTER TO the NEXT hour.

8:45 — Quarter to nine (15 minutes to 9 o'clock)
3:45 — Quarter to four (15 minutes to 4 o'clock)

Time Units

Unit	How Long
1 minute	60 seconds
1 hour	60 minutes
1 day	24 hours
1 week	7 days
1 month	28, 29, 30, or 31 days
1 year	365 days (or 366 in a leap year)

Converting Time

2 hours = 120 minutes (2 × 60)
3 days = 72 hours (3 × 24)
2 weeks = 14 days (2 × 7)

AM and PM

AM: Morning time (from 12:00 midnight to 11:59 noon)
- 8:00 AM = 8 in the morning
- 11:30 AM = Half past eleven in the morning
PM: Afternoon and night time (from 12:00 noon to 11:59 midnight)
- 2:00 PM = 2 in the afternoon
- 9:00 PM = 9 at night

Daily Schedule (Example)

Time	Activity
6:30 AM	Wake up
7:00 AM	Breakfast
8:00 AM	School starts
12:00 PM	Lunch break
3:30 PM	School ends
5:00 PM	Play time
8:00 PM	Dinner
9:00 PM	Bedtime

The Calendar

Days of the Week

Day	Number
Sunday	1
Monday	2
Tuesday	3
Wednesday	4
Thursday	5
Friday	6
Saturday	7

Months of the Year

Month	Number of Days
January	31
February	28 or 29
March	31
April	30
May	31
June	30
July	31
August	31
September	30
October	31
November	30
December	31

Knuckle Trick for Months

Make a fist. The KNUCKLES are the months with 31 days. The SPACES between are months with 30 days (except February).

January (knuckle = 31) → February (space = 28/29) → March (knuckle = 31) → April (space = 30) → May (knuckle = 31) → June (space = 30) → July (knuckle = 31) → August (knuckle = 31) → ...

Leap Year

A LEAP YEAR has 366 days. February has 29 days instead of 28.

Leap years come EVERY 4 years
2024 was a leap year. 2028 will be the next!

Age Calculation

How Old Are You?

If you were born in 2016 and the current year is 2026:

Age = Current year - Birth year Age = 2026 - 2016 = 10 years old

Practice Problems

Riya was born in 2015. How old is she in 2026?
- 2026 - 2015 = 11 years old
Amit is 9 years old. He was born in which year?
- 2026 - 9 = 2017
A grandmother is 65 years old in 2026. When was she born?
- 2026 - 65 = 1961

Sequencing Events

Sequencing means putting events in the ORDER they happened.

Your Day in Sequence

Wake up
Brush teeth
Have breakfast
Go to school
Study in class
Have lunch
Play with friends
Return home
Do homework
Have dinner
Go to sleep

Before and After

Before lunch, I have breakfast
After school, I play
Before 2025 comes 2024
After December comes January

Timeline

A TIMELINE shows events in order with DATES:

2020: Started school 2022: Moved to a new house 2023: Got a pet dog 2024: Visited grandparents 2025: Learned to ride a bicycle 2026: Started Class 3

Common Mistakes

'Half past 8 is 8:00.' — No! Half past 8 is 8:30. 8:00 is 'eight o'clock.'
'There are 24 hours in a day, so 2 days = 24 hours.' — No! 2 days = 2 × 24 = 48 hours.
'Quarter to 5 is 5:15.' — No! Quarter TO 5 is 4:45 (15 minutes before 5). Quarter PAST 5 is 5:15.
'February always has 28 days.' — In a leap year, February has 29 days. Every 4 years!
'9 PM is in the morning.' — No! 9 PM is 9 at NIGHT. 9 AM is 9 in the MORNING.

Quick Self-Test

Q1: What time is it when the long hand is at 12 and short hand is at 7? A1: 7 o'clock.

Q2: If school starts at 8 AM and ends at 3 PM, how many hours are you in school? A2: 7 hours (from 8 AM to 3 PM).

Q3: How many days are in a week? A3: 7 days.

Q4: Which month comes after June? A4: July.

Q5: Rohan was born in 2017. How old is he in 2026? A5: 2026 - 2017 = 9 years old.

Q6: What is quarter past 2? A6: 2:15.

Q7: How many minutes are in 3 hours? A7: 3 × 60 = 180 minutes.

Q8: Name the months that have 31 days. A8: January, March, May, July, August, October, December.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Clock reading rules

O'clock: long hand at 12, short hand points to the hour · Half past: long hand at 6, short hand halfway between two numbers — read as 'half past [the earlier number]' · Quarter past: long hand at 3 (15 minutes after) · Quarter to: long hand at 9 (15 minutes before, short hand approaching the next hour)

The long hand tells MINUTES. Each number on the clock = 5 minutes (1→5, 2→10, 3→15, 6→30, 9→45, 12→00/60).

AM and PM

AM (Ante Meridiem): midnight 12:00 to noon 11:59 — morning hours · PM (Post Meridiem): noon 12:00 to midnight 11:59 — afternoon/evening/night · 8:00 AM = morning, 8:00 PM = night. Same clock time, completely different part of the day.

A trick: AM = 'After Midnight' (until noon). PM = 'Past Midday'. It's not perfect but helps children remember.

Calendar facts

1 week = 7 days (Monday to Sunday) · 1 month = 30 or 31 days (February: 28 or 29) · 1 year = 12 months = 365 days (366 in leap year) · Months with 31 days: Jan, Mar, May, Jul, Aug, Oct, Dec · Months with 30 days: Apr, Jun, Sep, Nov · February: 28 days (29 in leap year, every 4 years)

Knuckle trick for month days: Make fists. Knuckle = 31 days, gap = 30 days (except Feb). Start with left pinky knuckle (Jan=31).

Age calculation and sequencing

Age = Current year − Birth year (if birthday has passed this year) · Age = Current year − Birth year − 1 (if birthday hasn't come yet) · Event sequencing: arrange events from earliest to latest based on dates or times.

At Class 3 level, age calculation is simple subtraction. The 'birthday passed or not' nuance can be introduced gently.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ At half past, reading the hour as the number the short hand is CLOSER TO, not the number it has PASSED

✓ At half past 8, the short hand is BETWEEN 8 and 9 (closer to 9). But we say 'half past EIGHT' — the hour that has already passed. Rule: read the LOWER number.

WATCH OUT

✗ Confusing AM and PM — saying '8 o'clock' for both morning and night

✓ Always specify AM or PM. 8:00 AM is morning (school time). 8:00 PM is night (dinner time). If unsure, think: is the sun up? → AM. Is it dark? → PM.

WATCH OUT

✗ Counting months as all having 30 days

✓ Months have either 31, 30, or 28/29 days. Use the knuckle trick to remember. January (knuckle) = 31, February (gap) = 28/29, March (knuckle) = 31, and so on.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Clock reading

Read time from clock pictures; draw hands to show given time; convert between clock face and digital time

Questions

Calendar and events

Calendar reading; age calculation; sequencing events; days between dates

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Clock

Draw the clock hands for: Half past 3.

▶ Show solution

Short hand: between 3 and 4 (closer to 4). Long hand: at 6. This shows 3:30.

Q2EASY· AM/PM

You eat lunch at school. Is it AM or PM?

▶ Show solution

PM (after noon). Lunch is typically between 12:00 PM and 1:00 PM.

Q3EASY· Calendar

If today is Wednesday, what day will it be after 10 days?

▶ Show solution

After 7 days = Wednesday again. Remaining 3 days: Thursday, Friday, Saturday. After 10 days, it will be Saturday.

Q4EASY· Age

Riya was born in 2016. What is her age in 2026?

▶ Show solution

Age = 2026 − 2016 = 10 years. (Assuming her birthday has already passed in 2026.)

Q5MEDIUM· Sequence

Arrange these events in order from earliest to latest: (a) Lunch at 12:30 PM, (b) Waking up at 6:30 AM, (c) Dinner at 8:00 PM, (d) School starts at 8:00 AM.

▶ Show solution

Earliest to latest: (b) Waking up 6:30 AM → (d) School starts 8:00 AM → (a) Lunch 12:30 PM → (c) Dinner 8:00 PM.

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Clock: Short hand = hour, Long hand = minutes. Long hand at 12 = o'clock, at 6 = half past, at 3 = quarter past, at 9 = quarter to
•AM = midnight to noon (morning). PM = noon to midnight (afternoon, evening, night)
•Half past: long hand at 6. Read the LOWER hour number (short hand is between two numbers)
•1 week = 7 days. 1 month = 30 or 31 days (Feb = 28/29). 1 year = 12 months = 365 days
•Knuckle trick: knuckle months = 31 days, gap months = 30 days (except February)
•Age = current year − birth year. Sequence events by their date/time from earliest to latest

CBSE marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 5–6 marks in Class 3 Mathematics assessment

Question type	Marks each	Typical count	What it tests
Clock reading / Drawing (1 mark)	1	2	Reading time from clock face; drawing hands for given time (o'clock, half past, quarter past/to)
Calendar / AM-PM (1-2 marks)	1–2	2	Calendar questions (day of week, days between dates); AM/PM identification; age calculation

Prep strategy

Buy or make an analog clock with movable hands — practice setting times daily
Throughout the day, ask: 'What time is it now? Is it AM or PM?'
Keep a calendar in the child's room — let them mark important dates (birthdays, holidays, exams)
Sing the 'Months of the Year' song and use the knuckle trick for month days
Practice age math: 'Grandma was born in 1960. How old is she in 2026?'

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