#
**Time Zones**

The world experiences different times in different places. Here students will learn what time zone is, what is prime meridian, what is Greenwichâ€™s meantime, how many time zones in India, etc.

## What Is Prime Meridian?

To maintain the world time zone, the prime meridian is considered the standard longitude through which the time is measured.

The prime meridian is a 0Â° longitude that runs

from north to south. It is also known as

Greenwich Meridian as it passes through the

London suburb of Greenwich.

## What Is Greenwich Mean Time?

Greenwich Mean time is the time zone at 0Â° The longitude and the mean solar time at the Royal Observatory in Greenwich, London is counted from midnight.

We know that it took approximately 24 hours to complete one rotation from west to east for the earth. This means that in 24 hours, the world covers 360 Â° longitude.

## Prime Meridian Longitude:

This implies that in 1 hour, it covers the

The lines of longitude run between 180Â° W to 180Â° E.

As one moves:

- To the west (left) of the Prime meridian, the time is reduced from GWT.
- To the east (right) of the Prime meridian, the time is increased from GWT.

### Example:

Suppose the Time in Greenwich Is 1:00 PM. What Will Be the Time in the Place With a Longitude of 30Â°W?

### Solution:

We know that,

15Â° longitude = 1 hour

Therefore, 30Â°(15 Ã— 2) longitude = 2 (1 Ã— 2) hours

This implies that at 30Â°W, the time will be 2 hours less than the time in
Greenwich.

Therefore, the correct answer is 11:00 am.

## How Many Times Zones in India?

A time zone is a region that follows the same local time. As we know, the earth moves at 15Â° longitude every 1 hour. The earth is divided into 24 (15 Ã— 24 = 360) times zone.

There are 12 time zones on each side of the prime meridian (0Â°) which is between 7.5Â°W to 7.5Â°E.

As we move 15Â° longitude:

- To the east of the prime meridian, the time in that area increases by 1 hour.
- To the west of the prime meridian, the time in that area decreases by 1 hour.

## What Is the Standard Time in India?

India lies between 68.7Â°E longitude to 97.25Â°E longitude. According, to the world time zones, it falls under two time zones. To avoid confusion between two different times on Indiaâ€™s eastern and western sides, its standard time is fixed on the central longitude (82.5Â°E).

We know that 1Â° = 4 minutes.

Therefore, 82.5Â°E = 82.5 Ã— 4 minutes

= 330 minutes.

Therefore, India is 330 minutes or 5 hours and 30 minutes ahead of Greenwich.

**Addition and Subtraction of time**

## Question 1:

Rina Notices That the Time in Greenwich Is 12 Noon. She Wants to Call Her Friend Who Stays in a Place Whose Longitude Is 65Â°W. What Will Be the Time in That Place?

### Answer 1:

Step 1: We know that,

15Â° longitude = 1 hour = 60 minutes.

1Â° = 60 Ã· 15 = 4 minutes.

Therefore, 65Â° = 4 Ã— 65 minutes = 260 minutes.

Step 2: 60 minutes = 1 hour.

When we divide 260 by 60, we get 4 as the quotient and 20 as the remainder.

Therefore, 260 minutes is equal to 4 hours and 20 minutes.

Step 3:

Since the place is in the east of Greenwich, the time in that place will be 4 hours and 20 minutes less than the time in Greenwich.

Therefore, the required time is 7:40 am.

## Question 2:

If the Time in Greenwich Is 7 PM. What Will Be the Longitude of the Place Where the Local Time Is 1 PM?

### Answer 2:

Step 1: Difference in the time:

7 â€“ 1 = 6

Therefore, the difference in the time between Greenwich and that place is 6
hours

Step 2: We know,

1 hour = 15Â° longitude

6 hours = 15 Ã— 6

= 90Â° longitude.

Since the time is decreased, the place must be in the west.

Therefore, the required longitude = 90Â°W.

## Question 3:

Meena and Reena Are Two Sisters Who Live on Two Different Sides of Prime Meridian. Meena Lives in the Place of Longitude 45Â°E, and Reena Lives in the Place of Longitude 45Â°W. They Called Each Other When the Greenwich Mean Time Was 8:15 A.M. Calculate the Time in Each of Their Places.

### Answer 3:

Step 1:

We know that,

15Â° longitude = 1 hour = 60 minutes.

1Â° = 60 Ã· 15 = 4 minutes

. Therefore, 45Â° = 4 Ã— 45 minutes = 180
minutes.

Step 2:

We know that 60 minutes = 1 hour.

Therefore, 180 minutes = 180 Ã· 60 = 3 hours

Step 3:

Meena stays in the east of Greenwich. Therefore, the time in Meenaâ€™s place will be 3 hours more than the GMT.

The GMT = 8:15 am

Therefore, the time in Meenaâ€™s place = 11:15 am.

Step 4:

Reena stays in the west of Greenwich. Therefore, the time in Meenaâ€™s

place will be 3 hours less than the GMT. The GMT = 8:15 am

Therefore, the time in Meenaâ€™s place = 5:15 am.

## Question 4:

Liza Lives in India, and Her Aunt Lives in London. Her Auntyâ€™s Birthday Is on the 2nd of April. She Wants to Wish Her Aunt on 2nd April at midnight. At What Indian Time Should She Call Her Aunty?

### Answer 4:

The time in London is equal to the Greenwich mean time.

India is 5 hours and 30 minutes ahead of Greenwich. Therefore, in India, the
time will be 5:30 am.

**Time and Date Calendar**

## Question 5:

Riya Stays in the United Kingdom. She Called a Friend Who Stayed in India and learned that the Time in India Was 4:15 Am on 21st May. What Were the Time and the Date When She Called Her Friend? The United Kingdom follows the Greenwich Mean Time.

### Answer 5:

The time in the United Kingdom is equal to the Greenwich mean time. India is 5 hours and 30 minutes ahead of Greenwich. This means that when Riya calls her friend, the time in her place should be 5 hours 30 minutes less than 4:15 am.

The time is 11:45 pm on 20th May.

## Question 6:

Zoya and Saiqua Are Two Best Friends Studying In The Same School in India. Saiquaâ€™s Parents Decided to Shift to Doha, Which Is 51.5310Â°E Longitude. Calculate the Time Difference Between India and Doha.

### Solution :

According, to the world time zone, for each 15Â°E longitude, the time is 1 hour more than the Greenwich mean time.

It follows that in all the places with longitude varying from 37.5 to 52.5, the time will be 3 hours more than the GMT.

Therefore, Doha is 3 hours ahead of GMT.

India is 5 hours and 30 minutes ahead of GMT.

Therefore, the time difference between India and Doha is 2 hours and 30
minutes.