EXTERNAL

FUNCTION julday (mm, id, iyyy)

    FUNCTION fint(x)      ! The Fortran INT function
        LET fint = truncate(x,0)
    END FUNCTION

    LET igreg = 588829   ! 15 + 31*(10 + 12 + 1582)
    IF iyyy = 0 then
       PRINT "There is no Year Zero."
       EXIT FUNCTION
    END IF

    IF iyyy < 0 then LET iyyy = iyyy + 1
    IF mm > 2 then
       LET jy = iyyy
       LET jm = mm + 1
    ELSE
       LET jy = iyyy - 1
       LET jm = mm + 13
    END IF
    LET jd = fint(365.25 * jy) + fint(30.6001 * jm) + id + 1720995
    IF id + 31 * (mm + 12 * iyyy) >= igreg then
       LET ja = fint(.01 * jy)
       LET jd = jd + 2 - ja + fint(.25 * ja)
    END IF
    LET julday = jd

END FUNCTION