JD to Mayan

var MAYAN_COUNT_EPOCH = 584282.5;

function jd_to_mayan_count(jd)
{
    var d, baktun, katun, tun, uinal, kin;

    jd = Math.floor(jd) + 0.5;
    d = jd - MAYAN_COUNT_EPOCH;
    baktun = Math.floor(d / 144000);
    d = mod(d, 144000);
    katun = Math.floor(d / 7200);
    d = mod(d, 7200);
    tun = Math.floor(d / 360);
    d = mod(d, 360);
    uinal = Math.floor(d / 20);
    kin = mod(d, 20);

    return new Array(baktun, katun, tun, uinal, kin);
}