Javascript unix timestamp to date time conversion

unix_to_datetime.js

let unix_timestamp = 1599629512236
// Create a new JavaScript Date object based on the timestamp
// multiplied by 1000 so that the argument is in milliseconds, not seconds.
var date = new Date(unix_timestamp);
// Hours part from the timestamp
var hours = date.getHours();
var day = date.getDate();
// Minutes part from the timestamp
var minutes = "0" + date.getMinutes();
// Seconds part from the timestamp
var seconds = "0" + date.getSeconds();

// Will display time in 10:30:23 format
var formattedTime = day + ':' + hours + ':' + minutes.substr(-2) + ':' + seconds.substr(-2);