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A Recap on the Time Zones
Since the earth rotates around its axis once every 24 hours, there are 24 time zones around the
earth, with 1-hour difference between them. Since the earth rotates through 360 degrees in 24
hours, it must rotate through 15 degrees of longitude in 1 hour (360° ÷ 24 = 15°). Therefore, each
of the 24 time zones is 15 degrees wide. Every place within a time zone has the same time, referred
to as its standard time.
With the development of rapid railway transportation, in the second half of the 1880s, the need for
standard time zones became obvious to Sir Sanford Fleming, Canada’s most experienced railway
surveyor and civil engineer. He wrote to the major governments of the world proposing the use of
time zones. In 1884, an international conference was held in Washington, D.C. to approve
Fleming’s system. It adopted the meridian that runs through the Royal Observatory in Greenwich,
England as the prime, or zero, meridian.
The prime meridian is the centre of a time zone that extends 7.5 degrees on either side. Time in
this zone is called universal time (UT – Universal time was formerly called Greenwich Mean Time
(GMT). Some people still refer to time in this zone as GMT.) and the standard times in other zones
are compared to it. Every 15 degrees, on either side of the prime meridian, is the centre of a time
zone.
Since the earth rotates from west to east, time zones that are east of the prime meridian have local
times that are ahead of UT. Time zones that are west of the prime meridian have local times that
are behind UT. For example, if the sun is directly above the prime meridian, the local time in the
city of Berlin, which is one time zone east of UT, is 1 p.m. In Ottawa, which is five times zones
west of the prime meridian, the time is 7 a.m. It will be five more hours before the sun appears
directly over the 75°W meridian, which is the centre of the time zone where Ottawa is located.
Countries, however, may modify the shape of the time zones and the standard) or legally
recognized) time they use. For example, China has one standard time for the whole country
despite the fact that it covers more than 60° of longitude. Canada, on the other hand, has six
standard time zones. The boundaries of the zones, however, do not follow exactly the meridians of
longitude.
Countries modify the shapes of the time zones for political reasons. For example, it may be more
convenient to have all of a province in one time zone. Time zones may also be adjusted so that they
do not pass through a city. Imagine the confusion that would arise if half a city was in one time zone
and the other half was in another time zone.
Some places are located where time zones meet. St. John’s, Newfoundland, at 52.18°W, is located
between the third and fourth time zones west of the prime meridian so its time is 3.5 hours behind
UT.
Canada’s Six Time Zones
Time Zones
Newfoundland Standard Time
Atlantic Standard Time
Eastern Standard Time
Central Standard Time
Mountain Standard Time
Pacific Standard Time
Number of Hours
Behind Greenwich
in Standard Time
3.5
4
5
6
7
8
Number of Hours
Behind Greenwich
in Daylight Time
2.5
3
4
5
6
7
Seen in Figure 1 is an illustration of the locations of Canada’s time zones
The International Date Line
When sailors first sailed around the world, they returned home either a day ahead or a day behind
those people who stayed. To correct this situation, the International Date Line was established.
The International Date Line was arbitrarily chosen to separate one day from the next. It has a very
convenient location, being in an unpopulated area of the world – the Pacific Ocean. It runs
between the North and South Pole, and generally follows the 180° line of longitude through the
Pacific Ocean. It zigzags, however, to avoid dividing land masses or island groups that belong to the
same country. It is generally a full 180° east or west of the Prime Meridian, on the opposite side of
the globe.
If you cross the date line moving westward, you add a day. If you cross the date line moving
eastward, you lose a day. The time does not change unless the date line corresponds to a time zone
boundary. West of the International Date Line is one day later than to the east of the line.
Consequently, someone who flies from Vancouver to Hong Kong may leave in the evening of
Sunday and arrive on Tuesday morning, after a 13-hour flight, having “missed” Monday1 The
reverse is true on the 13-hour return flight: having left Hong Kong on Monday evening, the flight
arrives in Vancouver on Monday morning just in time for the passengers to enjoy Monday morning
all over again.
The International Date Line just like the Prime Meridian runs through the middle of a time zone.
Seen in Figure 2 is an illustration of the International Date Line
Daylight-Saving Time
Many parts of the world change their time according to the season. Local standard time can be
determined for an area in the world by adding one hour for each time zone counted in an easterly
direction from one’s own, or by subtracting one hour for each zone counted in a westerly
direction. Occasionally, various countries that are some distance from the equator adjust the time
to take advantage of the early rise and late set of the sun, according to the season. We call this
practice “daylight saving time.”
In Canada, we move the clocks ahead one hour in spring to take advantage of longer evenings.
During the summer, daylight-saving time is used to extend daylight hours into the evening
when most people are awake. For example, the sun would set at 9 p.m. instead of 8 p.m., thereby
cutting down on energy use since lights don’t have to be turned on until later in the day. In fall, we
move the clocks back one hour in to provide more daylight hours in the morning. In Canada and
the United States, daylight-saving time begins on the first Sunday in April and ends on the last
Sunday on October. Other countries use different dates.
Time Zone Practice Calculations
Question 1: Calculate the time difference, in hours, between each of the following Canadian destinations:
(10 points)
A.
B.
Charlottetown and Toronto is _____________
Saint John and Saskatoon is _____________
C.
D.
E.
F.
G.
H.
I.
J.
Iqaluit and St. John’s is _____________
Sydney and Moose Jaw is _____________
Ottawa and Yellowknife is _____________
Edmonton and Montreal is _____________
Quebec City and Winnipeg is _____________
Regina and Moncton is _____________
Halifax and Victoria is _____________
Thunder Bay and Kenora is _____________
Question 2: A swim meet is being held next summer in your provincial capital. Swimmers will be
attending form Victoria, Brandon, Sault Ste. Marie, Medicine Hat, Saskatoon, Gatineau, Bathurst, Corner
Brook, Hamilton and Dawson. You are responsible for indicating the time difference between your
community and their community. Each team is expecting to receive this information by telephone at 9:00
a.m. local time. If you are calling from your community, at what time will you have to place each of these
calls? Remember to list your local time as a.m. or p.m.
(10 points)
K.
L.
M.
N.
O.
P.
Q.
R.
S.
T.
9 a.m. local time in Victoria = ________ Bedford Area
9 a.m. local time in Brandon = ________ Bedford Area
9 a.m. local time in Sault Ste. Marie = ________ Bedford Area
9 a.m. local time in Medicine Hat = ________ Bedford Area
9 a.m. local time in Saskatoon = ________ Bedford Area
9 a.m. local time in Gatineau = ________ Bedford Area
9 a.m. local time in Bathurst = ________ Bedford Area
9 a.m. local time in Corner Brook = ________ Bedford Area
9 a.m. local time in Hamilton = ________ Bedford Area
9 a.m. local time in Dawson = ________ Bedford Area
Time Zone Calculations Chart
Directions: All the information that you need to compete the time zone calculations can
be found in the chart below.
(10 points)
Flight
Departure Time
Toronto to
Calgary
Winnipeg to
Moncton
Quebec City
to San
Francisco
Victoria to
Regina
Edmonton to
St. John’s
10 a.m.
8:45 a.m.
Flight Duration
5 hours
2:40 p.m.
7 a.m.
Arrival Time
Before Time
Zone
Consideration
2 p.m.
Time Zone
Difference
- 2 hours
12 noon
+2 hours
6: 40 p.m.
4hours and 20
minutes
10 hours and
30 minutes
Arrival Local
Time
3:40 p.m.
+2 hours
6: 20 p.m.
Please Note: The time it takes to travel between two places is called the time distance.
To calculate the time distance you must add the total travel time.