int eraCal2jd(int iy, int im, int id, double *djm0, double *djm)
Gregorian Calendar to Julian Date.
Returned (function value): int status:
1) The algorithm used is valid from −4800 March 1, but this implementation rejects dates before −4799 January 1.
2) The Julian Date is returned in two pieces, in the usual ERFA manner, which is designed to preserve time resolution. The Julian Date is available as a single number by adding djm0 and djm.
3) In early eras the conversion is from the "Proleptic Gregorian Calendar"; no account is taken of the date(s) of adoption of the Gregorian Calendar, nor is the AD/BC numbering convention observed.
Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 12.92 (p604).
Copyright (C) 2013−2018, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.