The purpose of this book is to present, in a unified, completely algorithmic form, a description of fourteen calendars and how they relate to one another. Easy conversion among these calendars is a by-product of the approach, as is the determination of secular and religious holidays. Calendrical Calculations makes accurate calendrical algorithms readily available for computer use. This volume will be a valuable resource for working programmers, as well as a source of useful algorithmic tools for computer scientists. It also includes a wealth of historical material of value to anyone interested in chronology.