Page 192 - 9 teachers social book 9 @ 2077 ctp_Neat

The time after midnight is AM and time after noon is PM.
If both the places are to the east or west of prime meridian, subtract the longitude
to find out the longitudinal distance.
If one place is in the east and other is in the west of prime meridian, add the
longitude to find out the longitudinal distance.
As 24 hours make a day, the time of the day is counted on the basis of hours.
Such as 3 PM is 15:00 Hours, 10 PM is 22:00 Hours.

World Time Zone

Worked-out Example

What will be the time of Chicago located 88°W longitude, when it is 10:44 PM
at Kolkata at 88°E longitude?

Here, the longitudinal distance between Chicago and Kolkata is: 88° + 88° = 176°.

Now,

We Know, 1° = 4 minutes
The time differences between Kolkata and Chicago
= 176 × 4 minutes = 704 minutes = 11 hours 44 minutes
As Chicago lies to the west of Kolkata, its time is late than the time of Kolkata.

∴ When it is 10:44 PM in Kolkata, the time in Chicago is
10:44 PM (22:44 hours)- 11:44 hours

= 11:00 hours or 11 AM.

Dynamic Social Studies - Book IX 192