The Calendar Read Free Page B

correction for several decades. Even Copernicus, a generation before Gregory’s correction, penned a section about the true length of the year in his Revolutions of Heavenly Spheres, published in 1543. This was the same treatise that offered a compelling theory overturning the age-old belief that the sun and the planets revolved around the earth.
    Gregory’s reform came after he appointed a calendar commission in either 1572 or 1574, led by the Bavarian mathematician Christopher Clavius (1537--1612), one of two quiet heroes of the Gregorian correction. The other was an obscure Italian physician named Aloysius Lilius (1510-1576), who actually devised the solution Gregory issued as a papal bull on 24 February 1582. This came almost exactly 316 years--and two and a half additional lost days--after Roger Bacon’s appeal to Clement IV.
     
    Today almost everyone takes the precision of our calendar for granted, unaware of the long threads spooling out from our clocks and watches backwards in time, running through virtually every major revolution in human science, all linked to the measurement of time. The thread largely runs through the West, since this is the source of the world’s civic calendar, but also casts lines of varying sizes and thickness outwards to China, India, Egypt, Arabia and Mesopotamia. Unwinding backwards, it pauses at Clavius and at Bacon; at the rush of knowledge coming from Islam and the East during the Middle Ages; at bloody wars fought over dates after Rome’s collapse; and at Rome at its height, when Julius Caesar fell in love with Cleopatra, an affair that gave the West its calendar. It moves back further still to the Egypt of the pharaohs, Babylon, Sumer and beyond, thousands of years before Roger Bacon penned his treatise to the pope, when an unknown man dressed in reindeer skins and clutching an eagle bone gazed at the sky and got an idea as radical in his day as anything Bacon thought of in his: to use the moon to measure time.
     
     

2 Luna: Temptress of Time
     
    He appointed the moon for seasons: the sun knoweth his going down.
Psalm 104:19, c. 150 BC
     
    Some 13,000 years ago, when the southern flank of the great Wurm icecap still touched the Baltic Sea, the Dordogne Valley in central France looked more like present-day Alaska than the leafy winegrowing hills of today. Sprawling herds of reindeer, bison and woolly rhino grazed on tundra and drank the water of bracingly cold streams. From limestone heights sabre-toothed tigers scanned the herds as eagles circled slowly thousands of feet up in the chilly air, looking for shrews, mice and Palaeolithic rodents now extinct.
    Perched on a small bluff near what is now the village of Le Placard, another creature gazed not at the deer and bubbling stream but skywards. A Cro-Magnon version of Roger Bacon, this hairy, reindeer-skin-clad man patiently waited for the moon to rise above the valley. He was about to revolutionize the way he and his people would view time.
    For several nights this Stone Age astronomer and time reckoner had been watching the pale orb in the sky wax and wane. He noted that it moved through a series of predictable phases, and that he could count the nights between the moments when it was full, half full and completely dark. This was useful information for a tribe or clan that wanted to use the silvery light to cook and hunt, or for calculating future events such as the number of full moons between the first freeze of winter and the coming of spring. For the calendar maker himself it was valuable information he could use to impress his family, his mate and his clan by predicting when the moon would next be full or would disappear, events that even today signal key religious ceremonies and celebrations.
    The man at Le Placard was hardly the first to use the moon as a crude clock. But on this particular night this Cro-Magnon did not merely gaze upwards and ponder the phases of the earth’s satellite. Turning from the sky, he