We take the measurement of time for granted, yet our lives are punctuated by dates: Ramadan, New Year, Halloween, Mother's Day, tax day, birthday, payday. Some events are worldwide holidays, while others are celebrated by only a few. At what point in history did humankind begin to organize time? How did the patterns of the sun, moon, and stars influence the way we mark our hours and days? When and how did we establish the cycles of time that make a season, a decade, a century, or a millennium? The calendar is an indispensable tool for ordering and recording events. Many cultures have developed independent calendar systems, and religions have also played their part in the story. The modern western calendar, accepted today as a global frame of reference, is the fruit of a long and tumultuous history. This richly illustrated book traces the scientific, technical, and political history of calendars: the story of time itself. Well-written, loaded with information, and with a rich assortment of illustrations, each Discoveries "RM" volume is a look at one facet of art, archaeology, music, history, philosophy, popular culture, science, or nature. These innovatively designed, affordably priced, compact paperbacks bring ideas to life and amplify our understanding of civilization in a new way.