Julian Calendar System. Julian dates (abbreviated jd) are simply a continuous count of days and fractions since noon universal time on january 1, 4713 bc (on the julian calendar). Adopted in 45 bce, the julian calendar was a groundbreaking innovation that served as the predominant calendar in western civilization for over 1,600 years.
The earth takes 365.2422 days to. The julian calendar was the system of dating followed from 46bc onwards.