A time zone is a region that has a standard time throughout it There are 24 times zones throughout the world Why do We Need Standard Time Before the late 1800s towns and cities would set their own times based on the sun ID: 737428
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Slide1
Time ZonesSlide2
What is a Time Zone?
A
time zone
is a region that has a standard time throughout it
There are 24 times zones throughout the worldSlide3
Why do We Need Standard Time?
Before the late 1800s, towns and cities would set their own times based on the sun
Due to the Earth’s rotation, each location’s time was differentSlide4
Why do We Need Standard Time?
When railroads and telecommunications began to improve, it became difficult for each location to have its own time
Table showing different times across the U.S. in 1857Slide5
Time Zones
In 1884, the international standard time system was establishedT
he
prime meridian
was also established passing through Greenwich, England at 0
°
longitudeSlide6
Time Zones
By the year 1900, almost everywhere on Earth used some form of standard timeSlide7
Time Zones
Since there are 360
°
of longitude around the Earth and 24 time zones, each time zone is approximately 15
°
of longitude wideSlide8
Time Zones
The prime meridian is at 0
°
longitude
The
international date line
, where new days begin, is at 180
°
longitudeSlide9
Time zone boundaries are irregular primarily due to political reasons – often it is helpful for a country to be completely within one time zone
Time ZonesSlide10
Time Zones
Some countries are so large that they span multiple time zones Notable examples include: The United States
Russia
Brazil
Russia’s different time zonesSlide11
Time Zones
Other large countries use single time zones that are larger than 15°
of latitude
Notable examples include:
China
IndiaSlide12
Time Zones
Many countries use daylight savings time (DST) during part of the yearTypically during DST, clocks are advanced one hour forward in the spring and adjusted back one hour in the fall
Blue = currently uses DST, orange = once used DST but not currently, red = has not used DST Slide13
Time Zones
There are six time zones in the United StatesFour time zones are in the continental United States:
Eastern
Central
Mountain
Pacific
The other two time zones are:
Alaska time
Hawaii timeSlide14
Determining Times
If you know your local time, you can determine what time it is across the worldSlide15
Determining Times
As you move east, add one hour to your time for each time zone you move through, for example:
3pm
4pm
5pm
6pmSlide16
Determining Times
Conversely,
a
s you move west, subtract one hour for each time zone, for example:
10a
m
11
a
m
12
pm
1
pmSlide17
Practice Questions