In article <firstname.lastname@example.org>, Graham Cooper <email@example.com> wrote:
> Feb 29 is slotted into the calendar every 4 years, once every 100 > years and once ever 400 years etc. as the Earth's orbit is not evenly > divided into 365 segments. > > Without Feb 29, winter would be summer on our 365.0 days/year calendar > within Eons! > > It takes 24 hours for the Earth to spin from Noon to Noon, but in that > time it travels 1/365th of an orbit, about 1 degree around the sun. > > So one Earth rotation is actually 24 hours * 364/365 (subtract > 1/365th) > > Roughly 1000 minutes in a day, 333 X 3 minutes.. > > So about 23 hours 57 minutes for the Earth to do a full rotation. > > It needs the extra 3 minutes to spin 1 degree more to face the sun at > the same angle as 24 hours previous. > > So 1 normal year = 24 hours * 365 days > But 1 rotation is a bit short of 24 hours > So there must be 366 rotations in 1 normal year. > > So on leap years... yep! 367 full Earth rotations! > > 366 days PLUS 1 full spin to keep the calendar in check as it rotates > around the sun, kind of like the moon does 1 extra spin per month with > 0 days. > > Herc
You're making this more complicated than it is. One day is the time required for the same point on the Earth to face the Sun again. Because of the Earth's motion around the Sun, and the sense of its rotation, the Earth rotates a little more than 360 degrees in one day. In a calendar year this adds up to one extra full revolution. So in a leap year (366 days) the Earth rotates about its axis 367 times.
Because the period of the Earth's orbit about the Sun is not an integral number of days, no calendar year is exactly equal to one orbital period. That's the reason for all the corrections that complicate the civil calendar. But all that is irrelevant to how many revolutions the Earth makes during a CALENDAR year.