- The zero degree longitude line or the Prime Meridian
passes through Greenwich, a suburb of London.
- The Prime Meridian not only divides the eastern
from the western hemisphere, but it is also where
longitude and time is measured from.
- It takes the earth 24 hours to make one complete
rotation, the earth turns 360 degrees. Dividing 360
degrees by 24 hours gives you 15 degrees. Therefore,
the earth is divided into 24 time zones, each of which
is approximately 15 degrees of longitude wide.
- Greenwich Mean Time (GMT) is whatever time it is
in the main time zone, or the Prime Meridian Time
Zone.
- The map shows the time zones recognized today.
Because Earth rotates from west to east, the hours
grow earlier from east to west. When it is 3:00 P.M.
in Moscow, it is noon in London.
- To determine the standard time for any time zone
in the world, add one hour for each time zone east
of Greenwich. Subtract one hour for each time zone
counted in a westerly direction from Greenwich.
- Look at the time zone map. The numbers along the
top of the map show what time it is in each of the
other time zones when it is noon at the Prime Meridian.
- Since the continental United States spans such
a great distance, it has been divided into four standard
time zones; Eastern, Central, Mountain and Pacific.
When it is 7:00 A.M. in New York, it is 4:00 A.M.
in Los Angeles.
- Notice that the boundaries of the time zones zigzag
across land areas. By general government agreement
adjustments may be made to keep countries, provinces,
or states in a single time zone to avoid confusion.
|
| The International Date Line is at 180 degrees longitude.
The time is the same on both sides of the International
Date Line, but the day is different. West of the International
Date Line (the eastern hemisphere) it is one day later
than it is east of the International Date Line (the western
hemisphere). |
