Another new year and same old conundrum
One year ends, another begins; this is how we discipline the flow of time into manageable units. But what sort of order does a calendar impose, and what is it based on?
A Brief History of Timekeeping: The Science of Marking Time, from Stonehenge to Atomic Clocks by Chad Orzel shows how the science to track the passage of time has obsessed every era and location.
Humans have explored the patterns and cycles of the sun, moon and stars in different combinations to mark time. While it may seem universal, the modern calendar of 12 (almost) equal months in a rigid sequence was shaped by thousands of years of theology and politics, but also astronomy: the seasonal motion of the sun and moon across the horizon and the variable lengths of day.
Humans divided the year into 12 segments, but the stars and planets are not so accommodating. If the moon went a little slower, to take exactly 30 days, and if Earth orbited the sun a little quicker, in 360 days, celestial timekeeping would be a breeze, there would be no irregular months, no need to remember that September has 30 days and July 31.
Between the sun and moon, something’s got to give. A perfect calendar where the solstices and equinoxes fall on the same dates is impossible to construct, though much effort has gone into it.
One way to deal with the incompatible cycles of the sun and moon is to forget the moon altogether. The ancient civil calendar of Egypt, with 360 days and 12 months in three seasons, did exactly this, hitched to the position of the star Sirius and the flooding of the Nile. The Roman or Julian calendar learnt from this to go with 365.25 days, with months between 30 and 31 days, and a leap year every four years with an extra day. This calendar brought much-needed stability to agricultural and astronomical events, synced with the civil months and seasons.
Still, calendar reform became a pressing issue for mathematically minded Christians who wanted to fix the date of Easter, with an English monk in 1297 describing the Julian calendar as ‘intolerable, horrible and laughable’. Pope Gregory XIII in 1572 set up a committee to settle the matter. The Gregorian calendar is most successfully synced with the tropical year, with a mere 26 seconds of difference; it will take 3,323 years before the date of the March equinox slips by a day.
In counterpoint to these calendars is the highly sophisticated system of Mayan timekeeping. There was a widespread notion that Mayan astronomers considered December 21, 2012 to be the end of the world, but this trivialises their complex astronomical and mathematical learning. Their numbers were based on 20s, rather than 10s, and their 260-day cycle has to do with the experience of light in the tropics, marked by ‘zenith crossing’ days when the sun is directly overhead. They didn’t have a concept of doomsday but imagined time in endlessly repeating cycles.
Calendars are social constructs, the book shows. We standardised railway schedules and time zones to facilitate industrial modernity, and we need this precision to keep our world ticking, but the eccentric orbits of celestial bodies don’t fully cooperate.
This piece appeared as an editorial opinion in the print edition of The Times of India.
END OF ARTICLE