Stephen Jay Gould examines the phenomenon of the millennium. He looks at the origins of the term in the Biblical prophecies of the Book of Revelation - if the six ages of man date from 4000BC, will 2000AD signify the end of time? Gould describes how the meaning of the word has evolved to its present day usage and tackles the debate over whether the millennium ends in 1999 or at the end of 2000AD. He also questions the human compulsion to impose our time-schemes on the universe and wonders how far can we go in applying our mathematical principles to nature. Existing methods of calculating time are all flawed to some extent and yet the complexities of lunar months, leap years, and the calculation of dates such as Easter, are part and parcel of our fascination with calendrics as both a hobby and an occupation.