1. Time Zone

2. Why use a TIME ZONE? Prior to the late nineteenth century, time keeping was a purely local phenomenon. Each town would set their clocks to noon when the sun reached its zenith each day. A clockmaker or town clock would be the "official" time and the citizens would set their pocket watches and clocks to the time of the town - enterprising citizens would offer their services as mobile clock setters, carrying a watch with the accurate time to adjust the clocks in customer's homes on a weekly basis.

3. Travel between cities meant having to change one's pocket watch upon arrival. However, once railroads began to operate and move people rapidly across great distances, time became much more critical. In the early years of the railroads, the schedules were very confusing because each stop was based on a different local time. The standardization of time was essential to efficient operation of railroads. Why use a TIME ZONE?

4. In 1878, Canadian Sir Sanford Fleming proposed the system of worldwide time zones that we use today. He recommended that the world be divided into twenty-four time zones, each spaced 15 degrees of longitude apart. Why use a TIME ZONE?

5. Since the earth rotates once every 24 hours and there are 360 degrees of longitude, each hour the earth rotates one-twenty-fourth of a circle or 15 degrees of longitude. Sir Fleming's time zones were heralded as a brilliant solution to a chaotic problem worldwide. Why use a TIME ZONE?

6. Coordinated Universal Time (UTC) Basis for civil time in many places worldwide The time broadcast across the world since 1972. It is popularly referred to as GMT and at times UT1. The time system used in aviation and is informally known as Zulu Time to avoid confusion about time zones and daylight saving time.

7. UTC is commonly referred to as Greenwich Mean Time (GMT) when not counting the precise accuracy regarding fractions of a second. GMT is a historical term that has been widely used in many ways. GMT was first adopted as the world’s time standard at the Washington Meridian Conference in 1884. GMT is no longer the basis for civil time but is now loosely interchanged with UTC to refer to time kept on the Greenwich meridian (longitude zero). Places such as the United Kingdom observe GMT during the non-daylight saving period. Coordinated Universal Time (UTC)

8. The use of GMT is no longer recommended in technical contexts because of its ambiguity. A day of GMT began at noon (12:00) in astronomical and nautical almanacs prior to 1925 (the day of UTC starts at midnight (00:00), unlike GMT). This reckoning of GMT is now called Greenwich Mean Astronomical Time and is no longer used. Coordinated Universal Time (UTC)

9. Daylight Saving Time (DST) – often referred to as "Summer Time", is a way of making better use of the daylight in the evenings by setting the clocks forward one hour during the longer days of summer, and back again in the fall.

10. The clock moves ahead (= losing one hour) in the spring when DST starts, and falls back one hour (= gaining one hour) when DST ends in the fall. To remember which way the clock goes, keep in mind one of these sayings: “spring forward, fall back” or “spring ahead, fall behind.”

11. Many countries in the northern hemisphere observe DST, but not all. Daylight saving time begins in the northern hemisphere between March–April and ends between September–November. Standard time begins in the northern hemisphere between September–November and ends between March–April.

12. Daylight saving time begins in the southern hemisphere between September–November and ends between March–April. Standard time begins in the southern hemisphere between March–April and ends between September–November. Many countries in the southern hemisphere may observe DST.