orbtimes variables JD and DJ

Julian Day Number JD began at 12:00 PM (noon) Universal Time on January 1, 4713 BC. the variable JD is an extended precision floating point number, with the fractional part determining fractions of a day with respect to Universal Time (UT).

// Sunrise Friday   6:2.257904 July 25 2025 (local day)  Julian 2460881.959901 (hours UT=11.037632 )        
// location is latitude 36.000000 longitude -90.000000 daylight offset 1.000000       
    dj = JulianDays(25, 7, 2025);                                                                               
    jd = trueJulianDays(dj);                                                                                    
    icheck = (fabs(jd-2460881.959901)<1.0);                                                                     
                          

/* in our system we work with a modified
julianDay from 1900
*/
extended trueJulianDays(extended jd)
{
return jd + 2415020;
}