era.jdcalf.md

eraJdcalf

[rv, iymdf, calendar] = ERFA.jdcalf(ndp, dj1, dj2)

Julian Date to Gregorian Calendar, expressed in a form convenient for formatting messages: rounded to a specified precision.

Given:

   ndp       int      number of decimal places of days in fraction
   dj1,dj2   double   dj1+dj2 = Julian Date (Note 1)

Returned:

   iymdf     int[4]   year, month, day, fraction in Gregorian
                      calendar

Returned (function value):

             int      status:
                        -1 = date out of range
                         0 = OK
                        +1 = NDP not 0-9 (interpreted as 0)

Notes:

1. The Julian Date is apportioned in any convenient way between the arguments dj1 and dj2. For example, JD=2450123.7 could be expressed in any of these ways, among others:

           dj1            dj2

       2450123.7           0.0       (JD method)
       2451545.0       -1421.3       (J2000 method)
       2400000.5       50123.2       (MJD method)
       2450123.5           0.2       (date & time method)

2. 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.

3. See also the function eraJd2cal.

4. The number of decimal places ndp should be 4 or less if internal overflows are to be avoided on platforms which use 16-bit integers.

Called:

   eraJd2cal    JD to Gregorian calendar

Reference:

Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 12.92 (p604).

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.