समय और कैलेंडर
Time and Calendar
Time is the one measurement that does not run on tens, which is why children find it hard. Sixty seconds make a minute, sixty minutes an hour, twenty-four hours a day. Reading a clock, converting between 12-hour and 24-hour notation and using a calendar are Class 3-5 skills.
Units and conversions
| Unit | Equals |
|---|---|
| 1 minute | 60 seconds |
| 1 hour | 60 minutes = 3600 seconds |
| 1 day | 24 hours |
| 1 week | 7 days |
| 1 ordinary year | 365 days |
| 1 leap year | 366 days |
| 1 decade / century / millennium | 10 / 100 / 1000 years |
12-hour and 24-hour clock
After 12 noon, add 12 to the hour: 4 p.m. = 16:00 | 12 midnight = 00:00
- a.m. covers midnight to noon; p.m. covers noon to midnight.
- 12 noon is written 12:00, and 12 midnight is written 00:00 or 24:00.
- Railway timetables use the 24-hour clock, which is why Class 5 textbooks use train times as the standard exercise.
Leap year
Divisible by 4 = leap year; century years must be divisible by 400
So 2024 is a leap year and 2100 is not, but 2000 was. February has 29 days in a leap year. The rule for century years is the part most candidates forget, and it is exactly the part CTET asks.
Elapsed time
The hardest time question for a Class 5 child is finding the gap between two times that cross noon or midnight. The safe method is to break the journey: from 10:40 a.m. to 12 noon is 1 hour 20 minutes, and from 12 noon to 2:15 p.m. is 2 hours 15 minutes, giving 3 hours 35 minutes in all. Subtracting the two clock readings directly is where children go wrong, because time does not carry in tens.
Calendar facts
- Months with 31 days: January, March, May, July, August, October, December.
- Months with 30 days: April, June, September, November.
- An ordinary year has 52 weeks and 1 odd day, so the same date falls one weekday later next year; a leap year shifts it by two.
- The Indian national calendar is the Saka calendar, which begins with the month of Chaitra.
✗ 2100 will be a leap year because it is divisible by 4. | ✓ A century year is a leap year only if it is divisible by 400, so 2100 is not.
संकेत: लीप वर्ष = 4 से विभाज्य, लेकिन शताब्दी वर्ष तभी जब 400 से विभाज्य हो।
One question per paper, most often on the leap year rule or on a 24-hour clock conversion inside a timetable problem. The century-year condition is the standing trap. A second common item asks for elapsed time between two clock times crossing noon or midnight, where candidates lose track of the a.m. and p.m. change. Practise these with train timings, since CTET uses that context repeatedly.
Frequently asked questions
What is the rule for a leap year?
A year divisible by four is a leap year, except century years, which must be divisible by 400. So 2024 and 2000 are leap years while 1900 and 2100 are not, and February has 29 days in a leap year.
How do you convert p.m. time to the 24-hour clock?
Add twelve to the hour for any time from 1 p.m. onwards, so 4 p.m. becomes 16:00 and 11 p.m. becomes 23:00. Times before noon keep the same hour, and 12 midnight is written as 00:00.
How many odd days are there in an ordinary year?
One. An ordinary year of 365 days contains 52 complete weeks and one extra day, which is why a given date falls one weekday later the following year, and two days later after a leap year.
60-second recap
- 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day.
- Add 12 to p.m. hours for 24-hour time; midnight is 00:00.
- Leap year: divisible by 4; century years must be divisible by 400.
- 31-day months: January, March, May, July, August, October, December.
- Ordinary year has 1 odd day; leap year has 2.