|Day of week
Calculations are correct for all dates in the current Julian Period which began at 12 noon, 1st. January 4713 BC and will end at 12 noon, 1st. January 3268 AD. Although the converter will show both Julian and Gregorian calendar dates throughout this range, it should be noted that the Julian calendar was first introduced in 45 BC and the Gregorian calendar was not implemented until 1582 AD. Original dates before this would obviously not have been expressed in these calendars.
You can look at an explanation of the code used to perform the conversion from day, month and year in the Gregorian calendar to a Julian Day number.
Please send comments to Robin O'Leary pdc at ro dot nu