Canada is divided into six time zones. Most areas of the country's provinces and territories operate on standard time from the first Sunday in November to the second Sunday in March and daylight saving time the rest of the year.^[1]

The divisions between time zones are based on proposals by Scottish Canadian railway engineer Sandford Fleming, who pioneered the use of the 24-hour clock, the world's time zone system, and a standard prime meridian.^[2]

The National Research Council (NRC) maintains Canada's official time through the use of atomic clocks.^[3] The official time is specified in legislation passed by the individual provinces. In Quebec it is based on coordinated universal time.^[4] The other provinces use mean solar time.^{[5][6][7][8][9][10][11][12][13][14]} The NRC provides both coordinated universal time and mean solar time in its signals.^[15] It makes time servers available for direct synchronization with computers. The Canadian Broadcasting Corporation aired a daily time signal, the National Research Council Time Signal, beginning November 5, 1939.^[16] The signal was discontinued on October 15, 2023.^[17]

The Government of Canada recommends use of the 24-hour clock (e.g. 16:26), which is widely used in contexts such as transportation schedules, parking meters, and data transmission.^[18] Speakers of Canadian French predominantly use this system, but most Canadian English speakers use the 12-hour clock in everyday speech (e.g. 4:26 pm), even when reading from a 24-hour display, similar to the use of the 24-hour clock in the United Kingdom.

• The Yukon Time Zone (GMT−09:00) covered Yukon from 1900 until 1966. In 1983, the zone (then covering only a small portion of Alaska) was restructured to cover most of Alaska and renamed the Alaska Time Zone.
• In 1988, Newfoundland observed "double daylight saving time" from April 3 until October 30, meaning that the time was set ahead by 2 hours.^[22] All of Newfoundland and southern Labrador, which observes GMT−03:30 as its standard time zone, observed GMT−01:30.^[23] This only happened in 1988 and the province now only adjusts its time by one hour for daylight saving time.

Four Canadian cities, by local ordinance, observed daylight saving time in 1916. Brandon, Manitoba, adopted it on April 17. It was followed by Winnipeg on April 23, Halifax on April 30, and Hamilton, Ontario, on June 4.^[24] Port Arthur, Ontario, was the first place in the world to introduce it, on July 1, 1908.

Daylight saving time is currently observed in nine of ten provinces and two of three territories, with exceptions in several provinces and Nunavut. Most of the province of Saskatchewan, despite geographically being in the Mountain Time Zone, observes year-round CST. In 2020, the territory of Yukon abandoned seasonal time change and moved to permanently observing MST year-round.^[25] Under the Constitution of Canada, laws related to timekeeping are a purely provincial matter. In practice, since the late 1960s DST across Canada has been closely or completely synchronized with its observance in the United States to promote consistent economic and social interaction. When the United States extended DST in 1987 to the first Sunday in April, all DST-observing Canadian provinces followed suit to mimic the change.

In 2019, the legislature of British Columbia began the process of eliminating the practice of observing daylight saving time in the province. On October 31, 2019, the government introduced Bill 40 in the legislature, which would define "Pacific Time" as "7 hours behind Coordinated Universal Time (UTC)".^[26] In a press release, the provincial government stated an intention to maintain alignment of clock time with Washington, Oregon, California, and Yukon.^[27] The move follows a consultation earlier in 2019, in which the province received over 223,000 responses, 93% of which said they would prefer year-round DST as compared to the status quo of changing the clocks twice a year.^[28][29][30] The premier of British Columbia discussed the issue with Yukon premier Sandy Silver, who said in October that he needs more consultation with Yukon stakeholders, and with Alberta and Alaska.^[31]

The latest United States change (Energy Policy Act of 2005) to daylight saving time, adding parts of March and November to when daylight saving time is observed, which began in 2007 was adopted by the various provinces and territories on the following dates:

• Ontario^[32] and Manitoba^[33] – October 20, 2005
• Quebec – December 5, 2005^[34]
• Prince Edward Island – December 6, 2005^[35]
• New Brunswick – December 23, 2005^[36]
• Alberta – February 2, 2006^[37]
• Northwest Territories – March 4, 2006^[38]
• British Columbia – March 31, 2006^[39]
• Nova Scotia – April 25, 2006^[40]
• Yukon – July 14, 2006.^[41] Year-round MST as of March 8, 2020.^[25]
• Newfoundland and Labrador – November 20, 2006, but officially announced on January 18, 2007^[42]
• Nunavut – February 19, 2007^[43]
• Saskatchewan – No official action was taken, as almost all of the province remains on CST year-round. However, the few places in the province that do observe daylight saving (Lloydminster and the surrounding area, which straddles the Alberta border and observes Alberta's Mountain Time – and Creighton, which observes daylight saving on an unofficial basis due to its proximity to the border with Manitoba) follow the aforementioned March–November schedule just like the other provinces and territories.

Data for Canada from zone.tab of the IANA time zone database. Columns marked with * are the columns from zone.tab itself.

• Lists of time zones
• Newfoundland's Daylight Saving Act of 1917
• 1972 British Columbia time plebiscite
• Effects of time zones on North American broadcasting
• National Research Council Time Signal
• Date and time notation in Canada