An interesting fact about the Julian calendar is that it designates every fourth year as a leap year, a practice that was first introduced by King Ptolemy III of Egypt in 238 B.C.E. A quirk about the Gregorian calendar is that the longest time between two leap years is eight years. The last time such a stretch was seen was between 1896 and 1904; it will happen again between 2096 and 2104.