Monday is Feb. 29 — the bissextle or “leap day,” an artifact that dates back to the year 46 B.C.
Back then, Julius Caesar took the advice of the learned astronomer Sosigenes of Alexandria, who knew from Egyptian experience that the tropical year (also known as the solar year) was about 365.25 days in length. So to account for that residual quarter of a day, an extra day — a leap day — was added to the calendarevery four years.
Dispatches From The Front 