Extend Date Object with new function using Namespace

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// Extend Date Object with new function using Namespace
//Date.prototype.daysBetween
Date.prototype.daysBetween = function (date1, date2) {
    //Get 1 day in milliseconds
    var one_day = 1000 * 60 * 60 * 24;

    // Convert both dates to milliseconds
    var date1_ms = date1.getTime();
    var date2_ms = date2.getTime();

    // Calculate the difference in milliseconds
    var difference_ms = date2_ms - date1_ms;
    //take out milliseconds
    difference_ms = difference_ms / 1000;
    var seconds = Math.floor(difference_ms % 60);
    difference_ms = difference_ms / 60;
    var minutes = Math.floor(difference_ms % 60);
    difference_ms = difference_ms / 60;
    var hours = Math.floor(difference_ms % 24);
    var days = Math.floor(difference_ms / 24);

    return days + ' days, ' + hours + ' hours, ' + minutes + ' minutes, and ' + seconds + ' seconds';
};

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