Story of Clocks and Calendars: Marking a Millennium

January 1, 2001, will mark the beginning of a new thousand-year period on earth. But our earth is more than four billion years old, and humans have lived on our planet for perhaps two hundred thousand years.So how can it be the year 2000? The answer is that it is the year 2000 only on the Gregorian calendar. On the Hebrew calendar, the year will be 5760. On the Muslim calendar, the year will be 1420. And on the Chinese calendar, it will be 4698. So what year is it really? It all depends on what calendar you use and when you started counting the years.

Here is the fascinating story of timekeeping: how, over thousands of years, calendars and clocks came to be.