1. What time is it???
World Time Zones
See pg 30 of Holt purple text

2. There are 24 time zones
The sun is not directly overhead at every place on Earth at the same time, so clocks are adjusted to reflect the difference in the sun’s position.

4. 8:00 am in DFW = 6:00 am in San Francisco = 9:00 am in New York City
GMT
Longitude is measured starting at the prime meridian, which passes through Greenwich, England.
Time is also measured from Greenwich, and is called Greenwich mean time (GMT).
For each time zone east of the PM, clocks are set 1 hr ahead of GMT.
For each hour west of the PM, clocks are set 1 hr behind GMT.
8:00 am in DFW = 6:00 am in San Francisco = 9:00 am in New York City

5. International Date Line
Halfway around the planet from Greenwich is the International Date Line.
It follows the 180 degree line of longitude, adjusting slightly so as not to divide small island countries.
Other time zones do not always follow lines of longitude exactly. Some time adjustments are made to follow political boundaries.

6. Daylight Savings Time
Fall Back (1 hour – 11 pm becomes 10 pm on the clock, but it still FEELS like 11 pm!)
Spring Forward (1 hour – 5 am becomes 6 am on the clock, but it still FEELS like 5 am!)
We adjust our clocks in the summer so that we have more daylight in the evening hours.
This started in World War I. What’s the advantage for wartime?