Hi, using dates before the year zero the values are wrong. From

Wrong values in years B.C. about ephemeris HOT 6 CLOSED

mivion commented on June 12, 2024

Wrong values in years B.C.

from ephemeris.

Comments (6)

mivion commented on June 12, 2024

Hi,

Thanks, this is a bug.

from ephemeris.

blucobalto commented on June 12, 2024

Hi,
below the "$ ns.julian.calc" changed that solves the bug of Julian date.
I hope.

Thanks a lot,
blu

$ns.julian.calc = function (date) {
    var centuries;
    var year;
    var month;
    var b = 0;
    var c;
    var e;

    /* The origin should be chosen to be a century year
     * that is also a leap year.  We pick 4801 B.C.
     */
    year = date.year + 4800;
    if (date.year < 0) {
        year += 1;
    }

    /* The following magic arithmetic calculates a sequence
     * whose successive terms differ by the correct number of
     * days per calendar month.  It starts at 122 = March; January
     * and February come after December.
     */
    month = date.month;
    if (month <= 2) {
        month += 12;
        year -= 1;
    }
    e = Math.floor ((306 * (month + 1)) / 10);

    // number of centuries
    centuries = Math.floor (year / 100);

    if (date.year <= 1582) {
        if (date.year == 1582) {
            if (date.month < 10) {
                b = -38;
            }
            if (date.month > 10 || date.day >= 15) {
                // number of century years that are not leap years
                b = Math.floor ((centuries / 4) - centuries);
            }
        }
        else { b = -38; } //**** additional line to fix the bug *****
    } else {
        b = Math.floor ((centuries / 4) - centuries);
    }

    // Julian calendar years and leap years
    c = Math.floor ((36525 * year) / 100);

    /* Add up these terms, plus offset from J 0 to 1 Jan 4801 B.C.
     * Also fudge for the 122 days from the month algorithm.
     */
    date.julianDate = b + c + e + date.day - 32167.5;

    // Add time
    date.julianTime = (3600.0 * date.hours + 60.0 * date.minutes + date.seconds) / 86400.0;

    date.julian = date.julianDate + date.julianTime;

    date.j2000 = 2000.0 + (date.julian - $const.j2000) / 365.25;
    date.b1950 = 1950.0 + (date.julian - $const.b1950) / 365.25;
    date.j1900 = 1900.0 + (date.julian - $const.j1900) / 365.25;

    return date.julian;
};