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Hello, the calendar shapes the lives of millions of people.

It's an invention that gives meaning to the passing of time that orders our daily existence.

It links us to the arcane movements of the heavens and the natural rhythms of the earth. It's both deeply practical

and profoundly sacred. But where does this strange and complex creation come from? Why does the

week last seven days but the year 12 months who named these concepts and through them

shaped our lives. The answers involve Babylonian astronomers and Hebrew

theologians, Roman emperors and English scholars. Isaac Newton for instance designed a calendar

said to be mathematically flawless but no one can understand it. Gregory the

13th seems to have got it right. With me to discuss the calendar are Robert Poole, reader in history at

St Martin's College Lancaster, and author of Times Alteration, calendar reform in early modern

England. Kristen Lippincott, deputy Director of the National Maritime Museum in Greenwich,

and Peter Watson, research associate at the McDonald Institute for Archaeological Research

at Cambridge University, and author of a terrible beauty, a history of the people and ideas that shaped the modern mind.

Chris and Lippincott, what were the first calendars based on?

Well, the best way to think about the calendar is to put yourself back in the shoes of ancient man and

you're sitting there in the middle of some field watching the daily rhythms.

And the first rhythm that you really notice, either than beyond day and night, is the waxing and wannings of the moon.

And you notice that every 28 days you've got a full moon back.

And almost all of the early calendars are lunar calendars.

In fact, we have lunar calendars dating back to 10,000 BC.

...