Time Duration And Calendar Notes & Questions | Class 5 Mathematics | Drishti OS

Time Duration And Calendar

The number of days in each month of a non-leap year.
To calculate the end time of an activity given a start time and a duration in minutes.
To calculate the end time of a longer activity given a duration in hours and minutes.

Month	Days
January, March, May, July, August, October, December	31
April, June, September, November	30
February	28 (29 in a leap year)

Memory trick: "30 days hath September, April, June, and November; all the rest have 31, except February alone."

Symbolic: If the added minutes make the total 60 or more, subtract 60 from the minutes and add 1 to the hour.

Example: 10:45 + 30 minutes → 45 + 30 = 75 → 75 − 60 = 15, hour + 1 → 11:15

Symbolic: Add the hours and minutes separately, then fix the minutes if they reach 60 or more.

Example: 03:20 + 2h 50m → hours: 3+2=5, minutes: 20+50=70 → 70−60=10, hour+1 → 06:10

A class starts at 09:30 and lasts 45 minutes. When does it end?

Step 1 — 30 + 45 = 75 minutes
Step 2 — 75 − 60 = 15 minutes, carry 1 hour
Step 3 — 9 + 1 = 10
Answer: 10:15

A train leaves at 05:40 and the journey takes 3 h 35 min. When does it arrive?

Hours: 5 + 3 = 8
Minutes: 40 + 35 = 75 → 75 − 60 = 15, carry 1 hour
Hours become 8 + 1 = 9
Answer: 09:15

Mistake	Why it happens	Fix
Writing minutes as 75 instead of carrying the hour	Treating time like ordinary decimal addition	Remember 60 minutes = 1 hour; always carry over
Mixing up which months have 30 vs 31 days	Not knowing the rhyme	Learn "30 days hath September..." by heart
Forgetting February's day count	Assuming all months are the same	February has 28 days (29 in a leap year)

How many days are in the month of June?
A movie starts at 6:15 and runs for 2 hours 30 minutes. When does it end?
A test begins at 10:50 and lasts 20 minutes. When does it end?
Stretch: If today is the last day of April, what date and month is it tomorrow?

Revision tip: Practice on an analogue clock face — move the hands physically to see the hour "carry over" happen.

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