Change the date to calculate the Julian Day Number (JD#) and day of the week, or vice versa. Be certain to a enter positive year (there are no negative years), then specify A.D. or B.C.; remember, there was no year 0 (zero) so 0 is not a valid year.
The default date is today's date
In the AutoSelect mode (the default mode), the civil calendar changes from Julian to Gregorian between October 4/15, 1582. For Julian civil dates after that date, as in England and colonies until 1753, select Use Julian Only. A Julian date is valid from January 1, 4713 B.C. to present. For Financial dates and legal dates, days between dates, days before a date or days after a date, day of the week for a given date in history, involving the last 2 centuries, use the AutoSelect mode. Be sure to see the information below the calculator for general information about the Julian and Gregorian (accepted as our current civil calendar) calendars. In this calculator, we have avoided the "time of day" factor. It is briefly discussed below. If you have the need for that, you can use our calendar date to Julian date and time calculator or our calendar date and time From Julian date calculator.