Here you can find the source of getNextDate(i)
Date.prototype.getNextDate = function(i){ return new Date(new Date().setDate(new Date().getDate()+i)); };
Date.prototype.getFullDate = function(separator) { separator = separator ? separator : '-'; return this.getFullYear()+separator+this.getMonthFormatted()+separator+this.getDayFormatted(); };
Date.prototype.getGMTOffset = function () { return (this.getTimezoneOffset() > 0 ? "-" : "+") + String.leftPad(Math.floor(this.getTimezoneOffset() / 60), 2, "0") + String.leftPad(this.getTimezoneOffset() % 60, 2, "0");
Date.prototype.getLastDate = function() { return new Date(this.getFullYear(), this.getMonth() + 1, 0).getDate();
Date.prototype.getLocalDateObject = function () { return new Date(this.toLocaleString())
Date.getToday = function() { var now = new Date(); return now.getMidnight(); }; Date.prototype.getMidnight = function() { return new Date( this.getFullYear(), this.getMonth(), this.getDate(), 0, 0, 0); };
Date.prototype.getNumberDate = function() { var month = this.getMonth() + 1; var day = this.getDate(); var year = this.getFullYear(); return month +"/"+ day +"/"+ year;
Date.prototype.getPreviousDate = function(i){ return new Date(new Date().setDate(new Date().getDate()-i)); };
Date.prototype.getSecondsFormatted = function(number) { var second = this.getSeconds(); return second < 10 ? '0' + second : second; };
Date.prototype.getSecondsTwoDigits = function() var retval = this.getSeconds(); if (retval < 10) return ("0" + retval.toString()); else return retval.toString(); };