NCERT Class 4 Maths · Chapter 12
Ticking Clocks and Turning Calendar
Leap years, days and dates, AM and PM, the 24-hour digital clock, and finding how much time has passed.
📌 What you’ll learn in this chapter
- Leap years and the number of days in a year
- Reading dates like 04/07/2024 (DD/MM/YYYY)
- 24 hours in a day, and AM and PM
- Writing time on a digital (24-hour) clock
- 1 hour = 60 minutes, with half an hour and quarter hours
🎂 Let’s Begin: A Rare Birthday
Meet Ishita. She was born on 29 February! This date comes only once every 4 years, in a leap year. In other years, she celebrates on 28 February or 1 March.
📅 Part 1: The Calendar
- A normal year has 365 days, and February has 28 days.
- A leap year has 366 days, and February has 29 days. Leap years come every 4 years: 2016, 2020, 2024, 2028, 2032…
- Months with 31 days: January, March, May, July, August, October, December. Months with 30 days: April, June, September, November.
💡 Knuckle trick
Make a fist. Count the months on your knuckles and the gaps between them: January (knuckle) = 31, February (gap) = 28/29, March (knuckle) = 31… Knuckles have 31 days!
Reading dates
15/08/1947 means day 15, month 08 (August), year 1947, which is India’s Independence Day!
Pattern: If the 5th of a month is a Tuesday, then the 12th, 19th, and 26th are also Tuesdays (add 7 each time).
🕗 Part 2: AM and PM
A day has 24 hours. The clock goes round twice.
- AM: from 12 midnight to 12 noon (morning)
- PM: from 12 noon to 12 midnight (afternoon, evening, night)
So “8 o’clock” can be 8:00 AM (going to school) or 8:00 PM (dinner time).
📟 Part 3: The 24-Hour Clock
| AM/PM | 24-hour (digital) |
|---|---|
| 12:00 AM (midnight) | 00:00 |
| 6:30 AM | 06:30 |
| 12:00 PM (noon) | 12:00 |
| 2:15 PM | 14:15 |
| 9:00 PM | 21:00 |
💡 Rule
For PM times (after 1 PM), add 12 to the hour: 5:40 PM → 17:40. For 24-hour times over 12, subtract 12: 19:00 → 7:00 PM.
⏱️ Part 4: Hours and Minutes
1 hour = 60 minutes
- Half an hour = 30 minutes
- Quarter of an hour = 15 minutes
- Three-quarters of an hour = 45 minutes
How long did it take? Tuition starts at 4:40 PM and ends at 5:25 PM.
4:40 → 5:00 = 20 min, and 5:00 → 5:25 = 25 min. Total = 45 minutes.
⚠️ Common mistake
Reading the hour hand as minutes. The short hand shows the hour, and the long hand shows minutes (each number = 5 minutes). The long hand on 3 means 15 minutes, not 3!
✏️ Practice Time
Try these on your own first, then check your answer below each question.
Q1. Is 2028 a leap year?
✅ AnswerYes (2024 + 4)
Q2. Write 3:30 PM in 24-hour time.
✅ Answer15:30
Q3. A film starts at 6:15 PM and lasts 1 hour 30 minutes. When does it end?
✅ Answer7:45 PM
Q4. Today is Wednesday. What day will it be in 10 days?
✅ Answer7 days later is Wednesday again, then 3 more days → Saturday
Q5. How many minutes are in 2 hours?
✅ Answer120 minutes
📘 NCERT Textbook Activity Help
Hints and answers for the activities in the textbook, page by page. Try each one yourself before looking at the answer!
Pages 175–176 · Leap years and datesFebruary, leap years, and ages
✅ Answer
1. February 2024 = 29 days, and February 2025 = 28 days.
2. 2016, 2020, 2024, 2028, 2032, 2036
3. A leap year has 366 days.
5. Depends on today’s date.
6. July 1 is a Monday, so the next Mondays are July 8 and July 15.
7. Laali (born 4 July 2014) is older than Chotu (born 4 December 2019) by 5 years 5 months. Laali turns 5 on 04/07/2019. Chotu’s 10th birthday is on 04/12/2029.
Page 177 · Biscuits and date patterns2. 2016, 2020, 2024, 2028, 2032, 2036
3. A leap year has 366 days.
5. Depends on today’s date.
6. July 1 is a Monday, so the next Mondays are July 8 and July 15.
7. Laali (born 4 July 2014) is older than Chotu (born 4 December 2019) by 5 years 5 months. Laali turns 5 on 04/07/2019. Chotu’s 10th birthday is on 04/12/2029.
Expiry dates and days
✅ AnswerQ8: Count the months and days from the manufacturing date to today (the age of the packet), and from today to the expiry date (how long it’s still safe).
Q9: The same date moves to a different weekday each month. Months with 31 days move it forward by 3 days, and 30-day months by 2. For example, if July 15 is a Monday, then August 15 is a Thursday.
Page 178 · A doctor’s dayQ9: The same date moves to a different weekday each month. Months with 31 days move it forward by 3 days, and 30-day months by 2. For example, if July 15 is a Monday, then August 15 is a Thursday.
Hours in a day
✅ AnswerCount the hours for each activity on the clock circle. From 6 o’clock morning to 6 o’clock evening is 12 hours, and from 6 o’clock evening back to 6 o’clock morning is another 12 hours. The total is 24 hours, one full day.
Page 180 · Time formatsFill in the table
✅ Answer9:45 AM = 9:45 hours · 11:20 AM = 11:20 hours · 3:00 PM = 15:00 hours · 5:20 PM = 17:20 hours · 8:00 PM = 20:00 hours
Pages 181–182 · Hours and minutesRaghav, Muneera, and Akira
✅ AnswerRaghav took 15 minutes. Homework ends at 10:45 AM. Muneera finishes at 5:00 PM.
Akira: reaches school 8:15 AM → assembly ends 8:30 AM → dance practice ends 8:50 AM → break ends 9:00 AM. Both are correct: 1 hour = 60 minutes. Half an hour = 30 minutes, and three-quarters of an hour = 45 minutes.
Page 183 · Let Us CheckAkira: reaches school 8:15 AM → assembly ends 8:30 AM → dance practice ends 8:50 AM → break ends 9:00 AM. Both are correct: 1 hour = 60 minutes. Half an hour = 30 minutes, and three-quarters of an hour = 45 minutes.
Who read the clock correctly?
✅ AnswerRani is right each time: 04:00, 05:35, 07:15. Raghu and Raghav mixed up the hands. They read the short hand’s number as minutes, or the long hand’s number as hours. Remember: the short hand shows hours, and the long hand’s number × 5 gives minutes.
In 5 minutes you can brush your teeth, wash your hands, or tie your shoes and pack your bag.
In 5 minutes you can brush your teeth, wash your hands, or tie your shoes and pack your bag.
👨👩👧 Tips for Parents
- Circle family birthdays on a calendar and count the days left.
- Read train or bus times in the 24-hour format together.
- Ask: “We leave at 4:45. The trip takes 30 minutes. When will we reach?”