Consider this situation: You live at 90 degrees west longitude in St. Louis, Missouri. You have a friend who lives at 135 degrees east longitude in Kyoto, Japan. You would like to call your friend on the telephone sometime during the day when you are both awake. Both of you normally wake up at 7 a.m. and go to bed at 10 p.m.
! Click the image to start the animation. The clock shows the time in St. Louis. Count time zones to calculate the range of times you could call Kyoto, or use the next and back arrows below to find a good time to call your friend.