code: function getIso8601String(timeMs) {
    var time = new Date();
    time.setTime(timeMs);
    return '' +
        time.getUTCFullYear() + '-' +
        leftPadNumber(time.getUTCMonth() + 1, 2, '0') + '-' +
        leftPadNumber(time.getUTCDate(), 2, '0') + 'T' +
        leftPadNumber(time.getUTCHours(), 2, '0') + ':' +
        leftPadNumber(time.getUTCMinutes(), 2, '0') + ':' +
        leftPadNumber(time.getUTCSeconds(), 2, '0') + 'Z';
  }
docs: Convert milliseconds since the epoch to an ISO8601 datestring.