Julian calendar

The Julian calendar, introduced by Julius Caesar in 45 BCE, was a system for measuring time that aimed to align the calendar year with the solar year. It has 365 days divided into 12 months, with an extra day added every four years (leap year) to account for the fact that a solar year is about 365.25 days long. While an improvement over previous calendars, it gradually became misaligned with the seasons due to its slight overestimation of the year length. Eventually, it was replaced by the Gregorian calendar in 1582, which corrected this discrepancy.