Arthur David Olson <arthurdavidolson@gmail.com> writes:

From The Economist: "Why time may be running out for the leap second"

| The first is simple, ancient and intuitive, and based on the rotation of | the Earth, under which each complete rotation (or, equivalently, each of | the Sun's apparent trips through the sky) counts as one day. Of course, these are actually not equivalent; they're different by a full day per year.