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TIME ZONESTime Zones were irrelevant for most of history because travel was slow. However, with the advent of the railroad in the United States during the latter half of the 1800s, the development of time zones became relevant and necessary. Accurate time was essential in order for trains to run on schedule and for passengers to know when trains would arrive and depart. THE CONCEPT OF TIME ZONESTypically, noon is assumed to be the approximate time of day when the sun is overhead. The problem is that the sun is not directly overhead at the same time for everyone on earth. Thus the idea of time zones was born. HOW BIG IS A TIME ZONEThe mathematical size of a time zone can be calculated this way:Earth is a sphere and is measured in degrees—360 degrees as with any round object. So, there are 360 lines or degrees of LONGITUDE that run NORTH and SOUTH. There are 24 hours in a complete day—this is the length of time for earth to make one complete turn (ROTATION). Divide 24 into 360. The answer is 15.So, each time zone in theory covers 15 degrees of longitude.There are 24 total times zones.24 time zones x 15 degrees = 360U.S. TIME ZONESThere are 6 time zones in the United States. Beginning in the east and moving west, they are EASTERN STANDARD TIME, CENTRAL STANDARD TIME, MOUNTAIN STANDARD TIME, PACIFIC STANDARD TIME, ALASKA STANDARD TIME, AND HAWAII STANDARD TIME.Examine the U.S. Time Zone map at the top of the next page. TIME ZONES OF THE UNITED STATESFollowing is an illustration of how the time varies among U.S. time zones. EST CST MST PST AST HST 8:00 PM 7:00 PM 6:00 PM 5:00 PM 4:00 PM 3:00 PM11:20 AM 10:20 AM 9:20 AM 8:20 AM 7:20 AM 6:20 AM Note that Central time, whether morning, afternoon, or night, is ALWAYS 1 HOUR BEHIND Eastern Time. Mountain Time is always 2 hours behind, and Pacific is always 3 behind.Note that the minutes are always the same, only the hour is different. Keeping the minutes the same greatly simplifies keeping track of time. The East is always ahead of the rest of the country as far as time is concerned because of the direction in which the earth rotates—in a COUNTER CLOCKWISE direction. The east is the first part of the country to see the rising sun each morning, and the east is also first to witness sunset each afternoon. Hawaii is last to see the sun rise and last to see it set. Each time zone has the same amount of day and night whether east or west. AM, PMFrom midnight to 12:00 noon is AM time. Morning timeFrom noon to midnight is PM time. Afternoon time PSTMSTCSTEST10:30 AM 11:30 AM 12:30 PM 1:30 PMMIDNIGHT marks the beginning of a new day.PSTMSTCSTEST9:OO PM Saturday10:00 PM Saturday11:00 PM Saturday12:00 AM SundayWHY ARE TIME ZONE LINE CROOKED INSTEAD OF STRAIGHTTime zone lines are not strait in order to simplify life and make it easier for people! Think about a town divided by a time zone line. It might be 10:30 in one part of town but only 9:30 in another part of town. How confusing might that be? Consequently, time lines have been drawn to avoid dividing cities and high population areas. Check the Central Time Zone map at the end of this document. It shows that time lines adhere somewhat to readings for longitude as you can see how long the Central Time Zone is from North to South. It also clearly shows that political decisions about time make for very crooked time lines.STANDARD TIMEStandard time is in sync with the sun. On standard time the sun will be highest in the sky at NOON in every time zone. DAYLIGHT SAVINGS TIMESome years ago our country opted to go on Daylight Savings Time during the warm months. (Originally, the purpose for DST was to conserve electric energy.)The United States (except Arizona) switches to DST usually on the 2nd Sunday in March and goes back to standard time in early November.Going on DST does not increase the length of a day or save any time. Rather when we SPRING FORWARD in March, we are shifting time so that we have an extra hour of daylight in the late afternoon but 1 less hour of daylight in the early morning. THE NUMBER OF HOURS OF DAY AND NIGHT IS NOT ALTERED…JUST SHIFTED. We will SPRING FORWARD to DAYLIGHT SAVINGS TIME in early March. THE INTERNATIONAL DATELINEThe IDL, when crossed, not only means that your watch must be adjusted by an hour but your calendar date also must also be adjusted.Check the illustration below. IDL West side of the IDL East side of the IDL 7:00 AM, Wednesday 8:00 AM, Tuesday2:50 PM, Friday 3:50 PM, Thursday6:03 AM, Sunday 7:03 AM, SaturdayIn theory the International Dateline would be opposite of the Prime Meridian or 180 degrees longitude. However, the IDL is crooked like most time zone lines—it was drawn to eliminate confusion for the people who live in that part of the world. SEE THE CENTRAL TIME ZONE MAP on the next page ................
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