Why is February such a short month, having only 28 or 29 days, whereas the other months have 30 or 31?
He also introduced the concept of the leap day, which adds a day to February every four years. The month of Quintilis was renamed 'July' to honor him for this calendar reform. Later, Caesar Augustus made a minor calendar reform. Under Julius Caesar's calendar, leap day came in the middle of the month and had the same date as the day before.
Caesar Augustus moved the leap day to the end of the month and gave it its own date. February was an unpopular month, because it contained an unpleasant religious observance, so he moved one day from February to the month of Sextilis, which was renamed 'August' in his honor, and now had the same number of days as Julius' month, July. Thus, February was left short.