Here you can find the source of AddDays(days)
Date.prototype.AddDays = function (days) { this.setDate(this.getDate() + parseInt(days)); return this.getFullYear() + "-" + (((this.getMonth()+1) < 10)?"0":"") + (this.getMonth()+1) +"-"+ ((this.getDate() < 10)?"0":"") + this.getDate(); }
Date.prototype.AddDays = function(amount) { var d = new Date(this.getTime()); d.setDate(this.getDate() + amount); return d; };
Date.prototype.addDay = function(){
this.setDate(this.getDate() + 1);
};
Date.prototype.addDay = function(day) { if (null == day || isNaN(day)) { return this; this.setDate(this.getDate() + day); return this; };
Date.prototype.addDay = function addDay () { var day = this.getDate(); this.setDate(day + 1); this.setHours(0); this.setMinutes(0); this.setSeconds(0); if (this.getDate() === day) { this.setDate(day + 2); };
Date.prototype.addDays = function (d) { if (d) { var t = this.getTime(); t = t + (d * 86400000); this.setTime(t); return this; };