Nodejs Utililty Methods Date Different

Number.prototype.diffDate=function(d2){
    var d1=this;
    var diff1=new Date(d1.dateFormat()).getTime();
    var diff2=new Date(Number(d2).dateFormat()).getTime();
    var msdiff=Math.abs(diff1-diff2);
    var daysDiff=Math.floor(msdiff/(1000*60*60*24));
    return daysDiff;

Date.prototype.diffDays = function (date) {
    var diffMs = (this.getTime() - date.getTime()); 
    return Math.round(diffMs / 86400000);
};

Date.prototype.diffHours = function (date) {
    var diffMs = (this.getTime() - date.getTime()); 
    return Math.round(diffMs / 3600000); 
};

Date.prototype.diffMinutes = function (date) {
    var diffMs = (this.getTime() - date.getTime()); 
    return Math.round(diffMs / 60000); 
};

Date.prototype.diffSeconds = function (date) {
    var diffMs = (this.getTime() - date.getTime()); 
    return Math.round(diffMs / 1000);
};

var ONE_HOUR_IN_MILLIS = 60*60*1000;
var ONE_DAY_IN_MILLIS = 24*60*60*1000; 
Date.prototype.differenceInYears = function(obj) {
    var diffDays = Math.round(Math.abs((this.getTime() - obj.getTime())/(ONE_DAY_IN_MILLIS)));
    var diffYears = Math.ceil(diffDays/366);
    return diffYears;
};
Date.prototype.differenceInDays = function(obj) {
    var diffDays = Math.round(Math.abs((this.getTime() - obj.getTime())/(ONE_DAY_IN_MILLIS)));
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