JSFiddle - React, Tailwind, and code Playground

HTML

<p id="start1"></p>
<p id="start2"></p>
<p id="end1"></p>
<p id="end2"></p>

JavaScript

var a = new Date();
  var year = a.getFullYear();
  var month = a.getMonth();
  if(month === 0){
	var startDate = new Date((year-1)+'-12-02 08:00 GMT');
	var endDate = new Date(year+'-'+(month+1)+'-01 08:00 GMT');
  }else{
	var startDate = new Date(year+'-'+month+'-02 08:00 GMT');
	var endDate = new Date(year+'-'+(month+1)+'-01 08:00 GMT');
  }
  
  document.getElementById("start1").innerHTML=startDate;
  document.getElementById("start2").innerHTML=startDate.getTime()/1000;
  document.getElementById("end1").innerHTML=endDate;
  document.getElementById("end2").innerHTML=endDate.getTime()/1000;