For JD (Julian Date) = 2457873 on the Gregorian Calendar, the
corresponding date and time is: 2017 Apr 29 at 12:00:00.000 - Sat
JD (Julian Day) Number For Gregorian Calendar Date = 2457873
There is a distinction to be made between the JD (Julian Date) and the JD
(Julian Day) Number. They are not exactly numerically equivalent but can
sometimes be confused as such.
The JD (Julian Date) corresponds to a specific date and time of day. It is
usually a fractional value and only equates to an integer value at noon on
the corresponding date, at which point it also equates to the standard JD
Number for that calendar date.
The JD (Julian Day) Number is ALWAYS an integer value. It is simply the
sequential serial count of the number of calendar days since the mathema-
tical origin of the respective calendar system to which it applies.
Every date on either the Julian or Gregorian calendar system has a unique
sequential Julian Day (JD) Number to distinguish it from every other date
on the calendar.