It is equivalent to what we call the solar calendar and the lunar calendar.
Julian calendar is the predecessor of the international Gregorian calendar. Most western countries adopted it in the16th century. In 46 BC, Julius Caesar, commander-in-chief of Rome, made it with the help of the Greek mathematician and astronomer Sosichini in Alexandria, Egypt, and it was implemented from BC 1 year to replace the old Roman calendar. So people call this calendar "julian calendar".
Julian calendar is a pure solar calendar with the tropic year as the basic unit. It divides the whole year into 12 months, odd months are big months with a length of 3 1 day, and bimonthly months are small months with a length of 30 days. Only February has 29 days in normal year and 30 days in leap year. There are 365 days a year and a leap every four years. Leap year has 366 days, with an average annual length of 365.25 days. After the compilation of julian calendar, Augustus, the successor of Julius Caesar, subtracted one day from February and added August (the Latin name of August is his name Augustus), and changed September 1 1 to abortion, and 10 and 12 to big month.
Julian calendar is 0.0078 days longer than 365.2422 days of the Tropic of Cancer, and 3. 12 days older than 400 years. From March 2 1 to March 1 1. 1500 years later, it was improved and revised by Pope Gregory XIII in 1582 and became the Gregorian calendar, which is still used today.