On Monday, January 5, 2015 6:09:51 AM UTC-8, Tim wrote:
This is great reading especially for the technically challenged like me. With my style of lake boating its more like " hey, let's go that away!"

Keep it coming though. This is all good to know...

Although the Egyptians knew nothing of daily rotation and the orbital motion of the Earth around the Sun, they realized that they could not base their year on a constant stream of 365 days. The flooding of Nile on which their culture depended coincided closely with the annual appearance of Sirius one morning hence their awareness of the brightest star in the celestial arena for practical reasons and the fact that it skips an appearance by one day after 4 years. In dynamical terms, the additional 24 hours represents the orbital distance the Earth needs to travel to bring Sirius back into view or what now has become the February 29th rotation. We omit 6 hours of orbital motion each non leap year as we gauge our day solely by daily rotation and this accumulates to roughly 24 hours of missing orbital distance at the end of 4 orbital circuits and 4 years.

It isn't really possible to continue with the narrative without an explanation which contains the leap day rotation and what it represents in dynamical terms. Perhaps another could explain it better and I have no objections to this however the facts will remain roughly the same.

The maritime tradition, much like astronomy, is among the most noble and ancient human endeavors in terms of sophistication so that people generally don't think of their ancestors in terms of primitive but rather look for the roots of contemporary traditions in older methods and insights. The rules governing navigation from boats to aircraft are one thing but the timekeeping systems on which navigation is based in something else and this requires some knowledge of the Earth's daily and orbital cycles.