The Julian day
for this SysTime at the given time. For example,
prior to noon, 1996-03-31 would be the Julian day number 2_450_173, so
this function returns 2_450_173, while from noon onward, the Julian
day number would be 2_450_174, so this function returns 2_450_174.
The Julian day for this SysTime at the given time. For example, prior to noon, 1996-03-31 would be the Julian day number 2_450_173, so this function returns 2_450_173, while from noon onward, the Julian day number would be 2_450_174, so this function returns 2_450_174.