DateTime.julianDay

long julianDay() @property const @safe pure nothrow @nogc

The Julian day for this

DateTime 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.