moment.now = function () {
    // Custom function that returns
    // the number of milliseconds 
    // since Unix epoch
}

const moment = require('moment'); 
  
moment.now = function () { 
    return +new Date(2018, 11, 24); // 24 November, 2018 
} 
  
console.log(moment.now())

const moment = require('moment'); 
  
moment.now = function () { 
    return +new Date(2020, 11, 24); // 24 November, 2020 
} 
  
console.log(moment.now())