AP HUMAN GEOGRAPHY TIME ZONES

LONGITUDE’S ROLE Longitude plays the most important role in telling time There are 360◦ of longitude (180◦ West and 180◦ East of Prime Meridian) Longitude lines are spaced 15◦ apart in both directions from the Prime Meridian

TIME ZONES Meant to make time more uniform as the earth spins on its axis. 12 pm. Is midday everywhere, when the sun is high in the sky. 12 midnight is night everywhere. This only happens as clocks change when one travels on either side of the Prime Meridian

TIME ZONES

INTERNATIONAL DATE LINE This occurs at 180 ◦ longitude and divides the world from pole to pole through the Pacific Ocean If traveling from Asia to America, you set the clock BACK 24 hours, and vice-versa

WHAT HAPPENED BEFORE? Solar Time was based on the position of the sun in the sky as the day progressed. This led to differences between localities for railways and communications Governments then synchronized clocks so travelers could easily adjust to time changes

U.S. TIME ZONES In 1883, four time zones were created in the United States: Pacific Standard Time (6:00 am) Mountain Standard Time (7:00 am) Central Standard Time (8:00 am) Eastern Standard Time (9:00 am)