Questioning the Millennium: A Rationalist's Guide to a Precisely Arbitrary Countdown, originally published in 1997, is a book by Stephen Jay Gould about the history, relevance, and meaning of the millennium. The book is divided into three chapters, titled "What?," "When?," and "Why?," each of which is in essence a long essay. In the revised edition, published in 1999, the book also includes two prefaces; one from the original edition, and one added during the revision.
The first preface, "Predicting: The Biggest Millennial Fallacy," discusses the impossibility of predicting the future of humanity. In the second, "Our Precisely Arbitrary Millennium," Gould explains his plan for the book: to look at "calendrics, astronomy, and history—not prediction or psychology." And throughout the book, he does exactly this.
Gould's first chapter, "What?," (subtitled "Redefining the Millennium: From Sacred Showdowns to Current Countdowns") deals with the history of the idea of a millennium, which is rooted in eschatology, a field of theology which Gould describes as "futuristic visions about a blessed end of time." Gould goes into a fair amount of historical detail to explain the reasons that the word millennium, originally describing a period of time between the Second Coming of Jesus Christ and the Last Judgement, has been applied to unrelated thousand-year periods. Gould also uses this chapter to examine the history of millenarian movements, from early Christianity to the Jehovah's Witnesses to the American Indian Ghost Dance movement.
The second chapter of the book is titled "When?" This chapter is an expanded form of the essay "Dousing Diminutive Dennis's Debate (or DDDD = 2000)," previously published in Natural History Magazine and Gould's book Dinosaur in a Haystack. The chapter keeps the essays title as a subtitle. This chapter addresses the question of whether centuries begin at the beginning of '00 years, such as 2000, or '01 years, such as 2001. Gould notes that this is an issue that has been debated at the last three century changes, at the least. The source of the whole problem was a sixth-century monk named Dionysius Exeguus, or, in English, Dennis the Short, hence the original name of the essay. Dionysius was in charge of the preparation of a chronology, and, among other mistakes, chose not to give us a year 0. Hence, the B.C./A.D. system is forever short one year. This is a mere summary of the issue, though. Gould goes into much greater detail in the book, weaving in the issue of the year of Christ's birth as well. He also suggests a few solutions to the question of when the millennium should be celebrated.
The final chapter of the book, "Why?," discusses why the millennium, and indeed our entire time-keeping system, is both so fascinating and so complex. Gould looks at the complicated history of the modern Gregorian calendar, as well as the ways in which various cultures have created linked solar and lunar calendars. Gould ends the book with a look at day-date calculation, the incredible skill of being able to tell the day of the week of an event merely by knowing the year. In fact, the very ending of the book consists of a rather touching story, but I won't give that away.
A few notes about the book as a whole: First, it is sprinkled throughout with full page prints of great medieval apocalyptic art. Second, Gould shows a greater amount of respect for the religious material he deals with than some might expect from an agnostic. To me, this respect was one of the most fascinating facets of the book.