Page 1 - CH1-LN-2-Mapping the earth

SAI INTERNATIONAL SCHOOL
SUBJECT- GEOGRAPHY

CLASS-VI
CH-1 LOCATING PLACES ON EARTH SUB TOPIC-3-TIME ZONES

LESSON NOTE
Why do we have Time Zones?
The Earth rotates 360° in 24 hours. So, every 15° of longitude corresponds to a time difference of 1
hour.
As the Earth rotates, different parts of the world experience day and night at different times. Time
zones are created to standardize the time across regions.

Local time Standard time
Time of a place dependent on the apparent Fixed time for places set by law of a country,
movement of sun. taken as a central meridian.
Differs from place to place. Same for the whole country.
Places on the same longitude have same local Places on the same longitude have different
time. standard time.
Decided by shadow of sun, Decided by time zones.

Indian standard time is fixed on the basis of the local time of 82.5 degree (central meridian) of our
country.
What is the International Date Line (IDL)?
The International Date Line (IDL) is an imaginary line that runs roughly along the 180° longitude,
opposite the Prime Meridian (0° longitude). It is not a straight line; it zigzags around political
boundaries to avoid splitting countries into different dates.