This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book deals with all time frameworks, with additional attention to the time unit that is one of the purest human inventions, with no connection to natural patterns, the introduction of the week. It explains basic chronological periods in the history of time, often closely linked to some of the standard basic periods in world history. The book also deals with time in hunting and gathering societies, and some of the first efforts to measure at least certain forms of time. Agriculture introduced new needs and new opportunities to deal with time. The book focuses on the great civilizations, in the classical period but also the post-classical centuries. It draws on new developments in the early modern centuries, which turns out to be a crucial period in the history of time.