# 4th Class Mathematics Time and Calendar Time and Calendar

## Time and Calendar

Category : 4th Class

LEARNIN OBJECTIVES

• learn about measurement of time (hour and minutes).
• identify the duration of day and night.
• study calendar with dates and days.
• express time, using the terms, ‘a.m.’ and ‘p.m.’

Historical Preview

In ancients times people used to tell the time by watching the position of sun in the sky. They invented Obelisks (slender, tapering, four-sided monuments) which were built as early as 3500 B.C. Obelisks were special because they used moving shadows to tell about the time. Later on Egyptians modified it and made Sundials.

QUICK CONCEPT REVIEW

Don't we talk about time all the time like:

Time to take a bath.

Time to eat food.

Time to sleep.

Wake up time.

So, “What is time?”

Just like you have length to measure your garden, height to measure how tall you are, weight for the mass of your body, time is a measure for events. Events that are happening now or that had happened before.

Like length, weight or height have units, Time also has units and those are years, months, weeks, days, hours, minutes and seconds.

To measure with hours, minutes and seconds we use clock. In a day we have 24 hours.

CLOCK AND TIME

A clock dial has 60 divisions. These divisions show minutes or seconds. There are 12 numerals marked from 1 to 12 on clock face which are at an equal distances. 5th division is marked with 1, 10th division with 2 and so are 15th, 20th, 25th, 30th, 35th, 40th, 45th, 50th, 55th and 60th divisions marked with 3, 4, 5, 6, 7, 8, 9. 10, 11 and 12 respectively. These divisions, generally shown with longer lines than other divisions, represent hours (see the clock dial given)

The minute hand takes 60 seconds in moving from one division to next division. This is known as 1 minute.

60 seconds = 1 minute.

The minute hand takes 5 minutes in reaching from one marked numeral to next marked numeral. And in completing one full revolution it takes 60 minutes. This is called one hour.

60 minutes = 1 hour

An hour hand moves from one numeral to next numeral in 60 minutes.

Further we have seconds hand which takes 1 minute to complete one round. 60 seconds = 1 minute

There are few examples for you -

Amazing Facts

Months of the Year: Have you ever looked at the calendar and wondered where the names of the months came from? The origins of our calendar came from the old Roman practice of starting each month on a new moon. The Roman book – keepers would keep their records in a ledger called “Kalendarium” and this is where we get the word –Calendar.

CALENDAR

There is a way of measuring time in months, weeks or days and that is called a calendar. We have 12 months namely January, February, March, April, May, June, July, August, September, October, November and December. Some months have 30 days and some have 31 days. February is a month where we have 28 days but every leap year we have February with 29 days. To remember that which month has got 30 and 31doys we can use this poem.

30 days have September,

April, June and November,

All the rest have 31,

Excepting February alone.

Which only has but 28 days clear

and 29 in each leap year.

Further 7days makes a week. Name of the days are- Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday.

A poem for the days of the week:

Monday's child is fair of face

Tuesday's child is full of grace

Wednesday's child is full of cheer

Thursday's child is sweet and dear

Friday's child is loving and kind

Saturday's child is happy all the time

Sunday's child is honest and true

But the sweetest child belongs to you.

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