The Julian calendar was introduced by Julius Caesar in 45 BCE as a reform of the Roman calendar. It established a year consisting of 365 days divided into 12 months, with an extra day added every four years to create a leap year. This system aimed to align the calendar year with the solar year. Despite its improvements, the Julian calendar miscalculated the length of the solar year by about 11 minutes. This discrepancy led to a gradual drift of the calendar with respect to the seasons. Eventually, the Gregorian calendar was adopted in 1582 to correct this drift.