a leap of faith, ever four years

Why does February have less days?

The Roman calendar, which began in March and had only 10 months, was established by Romulus the founder of Rome in 753 B.C. His successor, Numa, changed this calendar into a proper lunar calendar, based on the Moon's phases. He also added the months January and February to the Roman calendar. Numa set aside the month of February for the religious festival of purification, which was the only month to have 28 days. The other months had 29 or 31 days, so that the cycle of the Moon's phases would coincide with the months. When Julius Caesar became dictator of Rome, he instituted the Julian Calendar, a true solar calendar based on the cycle of the Sun through the yearly seasons. To bring Numa's lunar calendar into accord with the Sun's annual cycle, 10 extra days needed to be added among the months. No extra days were added to February so as to not affect the pagan rituals performed during this month, so it remained a month of 28 days. Caesar's new calendar required an extra day every four years so he decreed that this day fall within February. And so we still to this day celebrate the "leap year" at the end of February.