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In the early days of formal timekeeping, determining the time was a specialized branch of astronomy. Now it is a branch of physics. Through decades of innovation, scientists at the Dominion Observatory and the National Research Council have created a Canadian time signal based not on the stars but on the cesium atom. This history of some 125 years of timekeeping in Canada documents a resolution in scientific principles and methods.Timekeeping in Canada originated in response to he needs of the mariner, the surveyor, the meterorologist, and the astronomer. Until the 1880s local time centres, serving regional needs, operated autonomously. The railways which linked the nation were one of the key factors in the gradual centralizatino of timekeeping responsibilities. The Dominion Observatory, established as a base for the survey of western Canada, gradually became of centre of research into modern techniques of timekeeping and in 1941 assumed resopnsibility for official time.This book reviews the advances adopted and often pioneered by the scientists at the Time Service in Ottawa, including the shift from astronomical to atomic time, short wave signal transmissions, and sophisticated astronomical measurements.The author was associated with the Dominion Observatory in Ottawa for more than forty years. He has been personally involved in the story he records, and the result is a rich blend of history, science, and anecdote.