Julian calendar, system of time measurement widely used between 46 B.C. and 1582. It was named for Julius Caesar, who devised it. The Julian calendar was based on solar cycles. The year was divided into 12 alternating 30- and 31-day months, with Feb. (29 days) being the exception. The Julian year was 11 min. and 14 sec. longer than the annual solar cycle, resulting in a discrepancy of 10 days by 1582. Pope Gregory XIII corrected the problem, bringing his Gregorian calendar into synchronization with the solar year.
See also: Calendar.