Julius Caesar introduced the Julian Calendar in 46 BC to replace the old Roman calendar, which was based on a lunar cycle.

A year in the Julian Calendar was 365 days long, with an extra day added every four years to account for the Earth's orbit around the Sun.

The extra day added to the Julian Calendar every four years was known as leap day, intercalary day, and bissextile day.

The Julian Calendar began on January 1, 46 BC, replacing the old Roman calendar.

The Julian Calendar was replaced by the Gregorian Calendar in 1582 AD, which is still the calendar used today.

The Julian Calendar was introduced to align the calendar with the Sun's cycle, make the calendar more accurate, and simplify the calendar.

A Julian year consisted of 365 days, with an extra day added every four years to account for the Earth's orbit around the Sun.

The average length of a Julian year was 365.2422 days, which is slightly longer than the actual length of the Earth's orbit around the Sun.

There were 25 leap years in a Julian century, which is a period of 100 years.

February was added to the Julian Calendar as an extra month to account for the Earth's orbit around the Sun.

In a leap year, February had 29 days instead of the usual 28 days.

Sunday was added to the Julian Calendar as an extra day to account for the Earth's orbit around the Sun.

A Julian week consisted of 7 days, just like the week we use today.

January was the first month in the Julian Calendar, and it is still the first month in the Gregorian Calendar.

December was the last month in the Julian Calendar, and it is still the last month in the Gregorian Calendar.