©G Dear 2009 – Not to be sold/Free to use General Mathematics HSC Spherical Geometry Time Zones Stage 6 - Year 12 Press Ctrl-A ©G Dear 2009 – Not to be sold/Free to use

Time zones are calculated in relation to GMT. Greenwich Mean Time For locations to our east we add time. Sydney = Adelaide + 30min = 9am + 30min = 9:30 am Adelaide 9am Sydney 9:30am Map

Time zones are calculated in relation to GMT. Greenwich Mean Time For locations to our east we add time. For locations to our west we subtract time. Perth = Adelaide – 1hr 30min = 9am - 1hr 30min = 7:30 am Perth Adelaide 9am 7:30am Map

Time Zone (2/9) If it is 7:08am [07:08 hrs] hours in London … … what time is it in Sydney? Sydney = London + 10hr [East] = 07:08 + 10hr = 17:08 = 5:08 pm Map

Time Zone (3/9) If it is 10:20am [10:20 hrs] hours in Sydney … … what time is it in Honolulu? Honolulu = Sydney - 20hr [West] = 10:20 - 20hr = -10:20 + 24:00 = 14:20 yesterday = 2:20 pm yesterday Map

= 10:20 + 4 hr [Crossing ‘Date Line’ subtract one day] = 14:20 Time Zone (4/9) If it is 10:20am [10:20 hrs] hours in Sydney … … what time is it in Honolulu? Honolulu = Sydney + hr [East] = 10:20 + 4 hr [Crossing ‘Date Line’ subtract one day] = 14:20 = 2:20 pm yesterday Map

When crossing the International Date Line… Time Zone (5/9) When crossing the International Date Line… going east – subtract one day going west – add one day When determining time zones 1o in longitude equals 4 minutes. 15o in longitude equals 1 hour. Map

USA Time Zones (6/9) Time Zone = -75 x 4 mins = -300 mins = -5 hrs 75oW Time Zone = -75 x 4 mins = -300 mins = -5 hrs Map

USA Time Zones (7/9) Time Zone = -90 x 4 mins = -360 mins = -6 hrs 90oW 75oW Time Zone -5 = -90 x 4 mins = -360 mins = -6 hrs Map

USA Time Zones (8/9) Time Zone = -105 x 4 min = -420 mins = -7 hrs 105oW 90oW 75oW Time Zone -6 -5 = -105 x 4 min = -420 mins = -7 hrs Map

USA Time Zones (9/9) Time Zone = -120 x 4 min = -480 mins = -8 hrs 120oW 105oW 90oW 75oW Time Zone -8 -7 -6 -5 = -120 x 4 min = -480 mins = -8 hrs Map