February 29, 2016. A Leap Day!

Statue of Pope Gregory XIII, in St. Peter's Basilica in Rome. Photo courtesy of Terez Anon.


Statue of Pope Gregory XIII, in St. Peter’s Basilica in Rome. Photo courtesy of Terez Anon.

By 2500 BC when the first of the Pyramids were built, the length of the year was reckoned by Egyptian mathematician/priests as 360 days. They had erected pairs of gnomons (posts with notches cut out at their tops) and positioned vertically so that at the Summer Solstice, light from the star Sirius, the brightest star in the Northern heavens, would be aligned in the notches. (Of course, the sun itself is a star, but it would not be identified as a star until Aristarchus introduced the heliocentric picture of the universe in the 3rd century BC, and Copernicus resurrected the idea in the mid-sixteenth century.) The Egyptian priests counted the days as Sirius wandered away, and then returned to the notches in the same pair of gnomons. Along with their determination of the length of the year, they introduced a year of 10 months of 36 days each. It is believed that they also introduced the number of degrees in a circle at this time as 360°.

By 800 BC, the Etruscans, the predecessors of Romans on the Italian Peninsula, realized that the seasons were occurring at the wrong time of year, and that a considerable error had accumulated in the preceding two millennia since the Egyptian. They also reckoned 365 days to be a much better approximation for the length of the year. However, they stayed with the Egyptian 10-month calendar of 36 days each, but modified it by adding 5 days of festivities at the end.

Initially, the Romans continued with the calendar that had been developed by the Etruscans. But following their practice of naming children in their families with the first 4 children being assigned proper —> Read More