Nodejs Utililty Methods Time Calculate

Date.prototype.addTime = function ( time ) {
  this.setTime( this.getTime() + time );
};
Date.prototype.addMinutes = function ( minutes ) {
  this.setMinutes( this.getMinutes() + minutes )
};
Date.prototype.addHours = function ( hours ) {
  this.setHours( this.getHours() + hours );
};
...

Array.prototype.forEach.call(document.querySelectorAll('main > ul li'), function (el) {
  el.style.color = color(el.dataset.datetime);
});
function color (datetime) {
  if (!datetime) { return; }
  var date = new Date(datetime);
  var ago = (new Date() - date) / (8.64e+7 * 365); 
  var day = Math.ceil((date - new Date(date.getFullYear(), 0, 1)) / 8.64e+7);
  var hue = Math.floor(360 * day / 365);
...

Date.prototype.currentTimeColor = function() {
    return "#" + ((this.getHours() < 10)?"0":"") + this.getHours() + ((this.getMinutes() < 10)?"0":"") + this.getMinutes() + ((this.getSeconds() < 10)?"0":"") + this.getSeconds();
};

Date.prototype.dateTime = function() {
   var yyyy = this.getFullYear().toString();
   var mm = (this.getMonth()+1).toString(); 
   var dd  = this.getDate().toString();
   var hh = this.getHours().toString();
   var min = this.getMinutes().toString();
   var sec = this.getSeconds().toString();
   var time = (hh[1]?hh:"0"+hh[0]) + ":" + (min[1]?min:"0"+min[0]) + ":" + (sec[1]?sec:"0"+sec[0]);
   var date = (dd[1]?dd:"0"+dd[0]) + "/" + (mm[1]?mm:"0"+mm[0]) + "/" + yyyy;
...

Date.prototype.datetime = function() {
  var y = this.getFullYear();
  var M = this.getMonth() + 1;
  var d = this.getDate();
  var h = this.getHours();
  var m = this.getMinutes();
  var s = this.getSeconds();
  M = M < 10 ? '0' + M : M;
  d = d < 10 ? '0' + d : d;
...

Date.prototype.distance_of_time_in_words = function(to) {
  distance_in_milliseconds = to - this;
  distance_in_minutes = Math.round(Math.abs(distance_in_milliseconds / 60000));
  if (distance_in_minutes == 0) {
    words = "less than a minute";
  } else if (distance_in_minutes == 1) {
    words = "1 minute";
  } else if (distance_in_minutes < 45) {
    words = distance_in_minutes + " minutes";
...

Date.fromUnixTime = function(value) {
    return new Date(value * 1000);
};

Date.prototype.getDateTimeStr = function () {
  let month = this.getMonth() + 1;
  if (month < 10) month = '0' + month;
  let day = this.getDate();
  if (day < 10) day = '0' + day;
  return this.getFullYear() + '-' + month + '-' + day + ' ' + this.getTimeAmPm();
};

Date.prototype.getDigitalTime = function(){  
  if  (this.getHours() > 12){
    var hour = this.getHours() - 12;
    var ampm = "PM";
  }else{
    var hour = this.getHours();
    var ampm = "AM";
  if (this.getMinutes() < 10)
...

Date.prototype.getFormatTime = function (){
  var date = '';
  date += this.getFullYear() < 10 ? '0' + this.getFullYear() +'-' : this.getFullYear() +'-' ;
  date += this.getMonth() + 1 < 10 ? '0' + (this.getMonth() + 1) +'-' : (this.getMonth() + 1) + '-';
  date += this.getDate()< 10 ? '0' + (this.getDate()) : this.getDate() + ' ';
  date += this.getHours()< 10 ? '0' + (this.getHours()) +'-' : this.getHours() + ':';
  date += this.getMinutes() < 10 ? '0' + (this.getMinutes()) +'-' : this.getMinutes() + ':';
  date += this.getSeconds() < 10 ? '0' + (this.getSeconds()) : this.getSeconds();
  return date;
...