getRemainingTime.js

function getRemainingTime(endDate){
  // Time difference betwwen now and deadline in milliseconds
  let timeDifference = Date.parse(endDate) - Date.parse(new Date())
  let seconds = Math.floor( (timeDifference/1000) % 60 )
  let minutes = Math.floor( (timeDifference/1000/60) % 60 )
  let hours = Math.floor( (timeDifference *60*60) % 24 )
  let days = Math.floor( timeDifference/ (1000*60*60*24)  )
  return `Countdown ${days} Days, ${hours} Hours, ${minutes} minutes, ${seconds} seconds`
}

const deadline = "April 13 2019 23:59:59 GMT+0200"
console.log(getRemainingTime(deadline));