February 29 takes approximately 6 hours longer than 365 whole days. A leap day compensates for this lag, realigning the calendar with the Earth's position in the Solar System; otherwise, seasons would occur later than intended in the calendar year. The Julian calendar used in Christendom until the 16th century added a leap day every four years; but this rule adds too many days (roughly 3 every 400 years), making the equinoxes and solstices shift gradually to earlier dates. By the 16th century the vernal equinox had drifted to March 11, and the Gregorian calendar was introduced both to shift it back
Kurdish calendar by a leap year every fourth year. It starts with the exact first day of spring according to the Gregorian calendar (March 20 or 21). Like the Gregorian system, the Kurdish calendar divides the year into four seasons: Buhar, Tawistan or Hawín, Payiz and Zimistan. It divides the year into 12 months, each month into four weeks and every week into seven days. In the Kurdish calendar the first six months (comprising spring and summer) are each 31 days long, while the next five months (in fall and winter) are 30 days each. The last winter month, the 12th month