JSFiddle - React, Tailwind, and code Playground

JavaScript

var d1 = new Date('October 01 2014'.replace('th',''));
var d2 = new Date('November 01 2014'.replace('th',''));

d1.setHours(0,0,0,0);
d2.setHours(0,0,0,0);

var diff = Math.ceil((d2 - d1) / 86400000) + 1;

console.log(diff);