The official time reference for Canada comes from the National Research Council of Canada (NRC), but, with the exception of during wartime, the provinces and municipalities legislate the official time zone boundaries. Canada spans almost 90° of longitude and now uses six time zones covering four and a half hours. From west to east the time zones are: Pacific, Mountain, Central, Eastern, Atlantic and Newfoundland.

History

Up to the 1880s, municipalities used their own local mean solar time. For example, at a latitude of 49°, two municipalities would have differed in time by one minute for each 18 kms of east–west separation, with the easternmost municipality having the later time. Everyone agreed on this arrangement when an 18 km journey was considered long, arduous, unpredictable or rare. However, with the advent of railways, the multitude of municipal times became a significant aggravation for the traveller. Before he became chief engineer for the Canadian Pacific Railway, Sir Sandford Fleming spent one uncomfortable night in a railway station due to the time confusion when changing trains. Although many other travellers had likely had similar experiences, Fleming's personal experience seemed to inspire his search for a way of reducing confusion about time.

In England, both Dr. William Hyde Wollaston and Abraham Follett Osler promoted a system of universal time. England was the first country to adopt standardized time, with the railways forcing the issue. North American railways experimented with operating each line on uniform time. To reduce the remaining confusion at a union station, American Charles Ferdinand Dowd advocated geographic time zones for the railways. Fleming became a strong advocate of time zones to be used for all purposes. In 1883, North American railways adopted hour-wide time zones. Fleming's advocacy of time zones had its greatest effect in 1884 at an international conference in Washington, DC, called to select a prime meridian to be used for navigation. The conference agreed on Greenwich, England as the common reference for longitude and time, and attending countries rapidly implemented Fleming's plan of 24 time zones around the world, each 15° of longitude wide, with the first centred on the Greenwich meridian. Today, the implementation of Greenwich Time is officially referred to as Coordinated Universal Time, or UTC. Time zones in Canada are referred to as UTC-xh. For example, British Columbia time in the winter months is described as UTC-8h, meaning it is eight hours behind Coordinated Universal Time, while Newfoundland time is referred to as UTC-3h30.

Canada, like the rest of the world, now uses a modified version of Fleming's time zones. The boundaries conform to more convenient geographical or political boundaries. In Newfoundland, for example, the time zone differs by 30 minutes from the expected time zone.

Daylight Saving Time

In Canada, as in most middle latitudes countries, Daylight Saving Time (DST) is now commonly used. A pre-breakfast daylight hour can be "saved" for use after supper by the practice of turning the clocks ahead by one hour in the spring and setting them back by one hour in the autumn. It was introduced in Canada by the federal government in 1918 as a measure for increasing war production, emulating legislation in Germany and Britain.

Federal government regulation of DST lapsed with the end of the First World War. It had been a popular innovation that was appreciated beyond the benefits of increased productivity and reduced energy consumption. Municipalities in Canada came to regulate DST practice to reduce the confusion present when different businesses on the same street used different times. The provinces became involved, passing different sorts of time legislation, and since 1987 official time zones and DST have been regulated by the provincial, territorial and municipal governments. With the exception of a handful of municipalities, the vast majority of the country observes DST, the only notable exception being Saskatchewan. Saskatchewan observes Central Standard Time year round (despite technically being in the Mountain Standard Time zone).

From 1988 until 2006, for the parts of Canada that use DST, clocks followed the North American pattern of "spring forward" on the first Sunday in April and "fall back" on the last Sunday of October. Since March 2007, the standard North American period for DST has been from the second Sunday of March to the first Sunday of November, a change introduced by the United States in 2005 when President George W. Bush signed legislation calling for a change to the annual beginning and end of DST. The new schedule was introduced to save energy, with a resultant beneficial effect on the environment, the rationale being that people would not need to have their lights on as early in the evening. Despite predictions of reduced consumption, data to support evidence of energy savings has been elusive.

Canadian provinces and territories, like nations around the world, followed the American plan to alter the scope of DST. It was essential to do so for trade, travel and communications, particularly in light of the US being Canada's chief trading partner.