Moon Phaser

moon.js

function getMoonPhase(year, month, day){
    var c = e = jd = b = 0;
    if (month < 3) {
        year--;
        month += 12;
    }
    ++month;
    var c = 365.25 * year;
    var e = 30.6 * month;
    var jd = c + e + day - 694039.09; //jd is total days elapsed
    jd /= 29.5305882; //divide by the moon cycle
    var b = parseInt(jd); //int(jd) -> b, take integer part of jd
    jd -= b; //subtract integer part to leave fractional part of original jd
    b = Math.round(jd * 8); //scale fraction from 0-8 and round

    if (b >= 8 ) {
        b = 0; //0 and 8 are the same so turn 8 into 0
    }

    var phases = [
      'New Moon',
      'Waxing Crescent',
      'First Quarter',
      'Waxing Gibbous',
      'Full Moon',
      'Waning Gibbous',
      'Last Quarter',
      'Waning Crescent'
    ];

    return phases[b];
}

return getMoonPhase([year],[month_n],[day_n]);