Julian calendar

The Julian calendar, named after Julius Caesar, is a calendar system introduced in the year 45 BCE. It was the most widely used calendar system in the world until the 16th century. The Julian calendar is based on the new moon cycle and works by counting days, with a leap year every four years. A leap year adds an extra day at the end of February, making it 29 days long instead of 28. This helps to keep the calendar in sync with the seasons and the sun.