1. Units of Time Based on Astronomical Motions and Objects Day: New: Time required for the earth to complete one rotation. Week: Based on 7 celestial bodies observable to ancients, Sun Moon, and 5 planets: Mercury, Venus, Mars, Jupiter, and Saturn. Month: Based on time for Moon to complete one set of phases. Year: New: Time required for Earth to complete one orbit around the Sun. 1 year = 365.24 days The calendar year usually has 365 days. To account for the.24 days, once every four years there are 366 days, with the extra day added to the month of February.This is called a Leap Year A Leap Year is any year exactly divisible by 4 and/or any century year exactly divisible by 400. Old: Time between two consecutive sunrises Old: Time for one cycle of the seasons

2. 12 Noon Local Solar Time Sun rises in the east and moves westward Local Solar Time, LST

3. One Solar Day...

4. Time Zones Differ by One Hour 24 Time Zones Based on Longitude 15° of Longitude in width Time equal to LST at central meridian of time zone 1st Time zone centered on the Prime Meridian (24 hours in one day) (sun appears to move from east to west) (earth spins 15° in one hour)

13. Traveling Westward Go Back One Hour For Each Time Zone Crossed Traveling Eastward Go Ahead One Hour For Each Time Zone Crossed

14. 1:00PM 9/15 Atlanta, GA (EST) ___________ Tokyo, Japan (141°E) 7:00 AM 9/15 Beijing (Peking), China _____________ London, England0°E 116°E 3:00AM 9/16 11:00PM 9/14

15. Atlanta, GA Tokyo, Japan Moving Eastward, Moving Ahead in Time W E ?

16. Beijing, China London, England ? Traveling Westward Go Back in Time

17. 1:00PM 9/15 Atlanta, GA (EST) ___________ Tokyo, Japan (141°E) 7:00 AM 9/15 Beijing (Peking), China _____________ London, England0°E 116°E 3:00AM 9/16 11:00PM 9/14