1. Timezones

2. Timezones How many time zones are there?
Earth is divided into 24 time zones.
Why is Earth divided into time zones?
It takes about 24 hours to rotate once on its axis
Because Earth is constantly spinning, time is constantly changing

3. Timezones How are timezones divided?
Each timezone is about 15° wide, corresponding to longitude
However, some timezones have been adjusted in local areas
Why?
So that cities wouldn’t be split it half by a timezone!
Large countries often have several timezones

4. Timezones Open your textbooks to p. 30
The figure at the bottom of the page shows international time zones.
When it is 12pm in England, what time is it in Madagascar?
If it is 3pm in Argentina, what time is it in Hawaii?

5. Calendar Dates When do we switch from one day to the next?
Each day ends at the stroke of midnight
Each time you travel through a time zone, you gain or lose time, until at some point, you gain or lose an entire day
International Date Line - 180°meridian - serves as the transition line for calendar days
When you travel west across the Date Line, you advance your calendar one day
When you travel east across the Date Line, you move your calendar back one day

6. Pull out a Blank Sheet of Paper
Use the figures on page 30 and 31.
When it is 10am in Atlanta, Georgia, what time is it in Los Angeles, California?
It’s 2pm in Denver, Colorado. What time is it in Chicago, Illinois?
If it’s 2pm in New York, New York, what time is it in Quito Peru?
If it is 3pm on Thursday, July 4 in Salt Lake City, Utah, What time and day is it in Tokyo, Japan?
If it’s 10am in Syracuse, New York (76° W longitude), What time is it in Athens Greece (24° E longitude)?
Would a person flying from Virginia to California have to set his or her watch backward or forward? Explain.