3 Time ZonesWith the advent of rapid travel by trains in the 19th century, it became necessary to standardize the time for all cities within a certain region.In November 1883, the railroad companies divided the continental United States into four time zones: Eastern, Central, Mountain, and Pacific.Everyone in a time zone set their clocks to the same standard time.
4 Time ZonesIn 1884, an international conference was held in Washington D.C. by 26 countries.The world was divided into 24 time zones, with each zone being roughly 15 degrees wide in longitude.Since there are 24 hours in a day, and 360/24=15, the time in each zone differs from the time in adjacent zones by one hour.
6 Time ZonesBy international agreement, longitude is measured from the prime meridian.This meridian passes through the Royal Observatory in Greenwich, England.Time is measured from Greenwich, England and is called Greenwich Mean Time (GMT)For each time zone east of the prime meridian, clocks must be set one hour ahead of GMT.For time zones west of the prime meridian, clocks are set one hour back from GMT.
7 Time ZonesTime zones do not follow meridians exactly; political boundaries are often used to draw time zone lines.Times zones have been modified for political, social, and economic reasons.
8 Time ZonesInternational Date Line runs north-south through the Pacific Ocean at 180 degrees. This time is 12 hours from GMT.There is a time difference of 24 hours between the two sides of the 180 degree meridian. It is called the International Date Line because when you cross it the date and day change.
9 Cross from east to west – gain a day Cross from west to east – lose a day
10 Time Zone Changes Some countries have made changes. For example, most of the US has daylight savings time in the summer to have more evening hours of daylight.
11 A.M. and P.M. At midday, the Sun is on your meridian. this occurs close to, or at noon.A.M. comes from ante meridiem (before midday)P.M. comes from post meridiem (after midday)
12 Time Zone Practice If it is 12:00 P.M. in the Central Time Zone, what time is it in the PacificTime Zone?If it is 7:00 P.M. in the Eastern Time Zone, what time is it in the Mountain Time Zone?If it is 7:44 A.M. in the Pacific Time Zone, what time is it in the Central Time Zone?
13 WIO http://teachersites.schoolworld.com/webpages/NCouncil/ Draw a rough map of the continental United States.Divide the United States into the four continental time zones.Write and answer the following questions:If it is 1:00 P.M. in the Mountain Time Zone, what time is it in the Eastern Time Zone?If it is 10:00 A.M. in the Pacific Time Zone, what time is it in the Central Time Zone?If it is 4:00 A.M. in the Pacific Time Zone, what time is it in the Eastern Time Zone?