A Word about Dates

A Word about Dates

In 45 BC, Julius Cæsar, advised by the Helleno-Egyptian astronomer Sosigenes, replaced the ancient Roman lunar calendar with a ‘Julian’ solar calendar of 365¼ days beginning on the first of January of that year. Because the Julian calendar year was 11 minutes 14 seconds too long, it was remarked by the Middle Ages that the calendar erred for celebrating the dates of holy festivals and predicting the equinoxes and solstices.

It wasn’t until the Renaissance that European mathematics was sufficiently advanced to rectify this. So, in 1582, Pope Gregory XIII decreed advancing the Julian calendar by ten days and stipulating that only centenary years exactly divisible by 400 could be bissextile or leap-years. This became known as the Gregorian calendar, and was laboriously explained in an 800 page folio volume published by the Italian astronomer Clavius in 1603. The Gregorian calendar will be accurate until the year 3000, after which it will be wrong by one day.

The Protestant German States changed their calendars in 1700, but the constitutionally traditional Anglo-Saxon world didn’t effect a correction until 1752, when, by act of parliament, the Julian calendar was advanced by eleven days, September second being followed by September fourteenth. This resulted in riots in London, but the temporal authority of the House of Lords prevailed, and the new calendar was enforced. At the same time, New Year’s Day was changed from 25 March (nine months before Christmas Day) to 1 January. Orthodox Russia was the last European holdout, not changing its calendar until the Soviet government imposed the Gregorian revision after the Revolution.

Therefore, in 2014 and until 2100, to convert the days of Columbus’s calendar into modern dates, one must add thirteen days, so that 12 October becomes 25 October.

J Marvel, October, 2014.

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