The term "Julian date" is ambiguous. Do you want a date in the Julian calendar, the one which predated the Gregorian Calendar? Or do you want a Julian day number, which is the number of days elapsed since noon on 1 January 4713 B.C. (GMT). These are unrelated concepts, named after two different people. We can't provide a better answer without knowing which you mean. You may want to check out
this post however.