moment.js

gistfile1.js

// http://jquense.github.io/react-widgets/docs/#/datetime-picker
//
// <form>
//   [date]  [time]
// </form>
//
// Both fields return datetime format:
// To compine them in one
 
let dateField = "Fri Jun 12 2015 15:08:31 GMT+0200";
let timeField = "Wed Jun 10 2015 02:35:00 GMT+0200";

let date = moment(dateField).startOf("day");
let time = moment.duration(moment.utc(timeField));
let result = date.add(time, "millisecond").format();
console.log('result:', result); // result: 2015-06-12T02:35:00+02:00

// Convert from UTC to local
let datetimeField = "2015-06-25T21:30:00";
let result = moment(new Date(datetimeField)).format();
console.log('result:', result); // result: "2015-06-25T23:30:00+02:00" (for TZ +2)