The term Julian date may also refer, outside of astronomy, to the day-of-year number (more properly, the ordinal date) in the Gregorian calendar, especially in computer programming, the military and the food industry, … See more

Because the starting point or reference epoch is so long ago, numbers in the Julian day can be quite large and cumbersome. A more recent starting point is sometimes used, for instance by dropping the leading digits, in order to fit into limited … See more

As stated above, the Julian date (JD) of any instant is the Julian day number for the preceding noon in Universal Time plus the fraction of the day since that instant. Ordinarily calculating the fractional portion of the JD is straightforward; the number of seconds that have … See more

• Alsted, Johann Heinrich 1649 [1630]. Encyclopaedia (in Latin), Tome 4, Page 122.
• American Ephemeris and Nautical Almanac, … See more

Julian Period
The Julian day number is based on the Julian Period proposed by Joseph Scaliger, a classical scholar, in 1583 (one year after the Gregorian … See more

The Julian day number can be calculated using the following formulas (integer division rounding towards zero is used exclusively, that is, positive values are rounded down and negative values are rounded up):
The months … See more

• 5th millennium BC
• Barycentric Julian Date
• Dual dating
• Decimal time
• Epoch (astronomy) See more