JAVASCRIPT

date to seconds js

var date = new Date("2015-08-25T15:35:58.000Z");
var seconds = date.getTime() / 1000; //1440516958

javascript seconds to date

let sec = 1628618888939
let time = new Date(sec)
let normalDate = new Date(sec).toLocaleString('en-GB',{timeZone:'UTC'})
time: "Tue Aug 10 2021 21:08:08 GMT+0300 (Eastern European Summer Time)"
normalDate: "10/08/2021, 18:08:08"

js seconds to time

const secs2Time = (secs) => {
  const hours = Math.floor(secs / 60 / 60).toString().padStart(2, 0)
  return hours + ':' + new Date(secs * 1000).toISOString().substr(14, 5)
}