Designed to be an accessible history of the use and interpretation of time, Borst examines the ways that time has been calculated by numbers and measured by instruments through the ages from the computus - an ancient method of determining times and dates - to the present-day computer. In a wide-ranging discussion, he analyzes the classical Greek concepts of divine, natural and human time; the universal time of ancient Rome; the Easter cycle of the Middle Ages; the development of the mechanical clock in the 14th and 15th centuries; early modern chronology; and 20th-century data processing. Borst argues that although many centuries and countless different instruments separate the computus from the modern computer, each generation throughout the ages has had to answer the same question: how can we make the best use of our available time to improve our lives?