From the city sundials of ancient Rome to the era of the smartwatch, clocks have been used throughout history to wield power, make money, govern citizens and keep control. Sometimes, also with clocks, we have fought back. In this book, time expert David Rooney tells the story of timekeeping, and how it continues to shape our modern world. In twelve chapters, demarcated like the hours of time, we meet the greatest inventions in horological history, from medieval water clocks to monumental sundials, and from coastal time signals to satellites in Earth's orbit.