Timestamp Epoch

new Date().getTime();

Timestamp ISO 8601

function awsIsoDateTime(awsDate) {
  var awsYear  = awsDate.getYear() + 1900;
  var awsMonth = (awsDate.getMonth() < 9) ? ('0' + (awsDate.getMonth() + 1)) : (awsDate.getMonth() + 1);
  var awsDay   = (awsDate.getDate() < 9) ? ('0' + awsDate.getDate()) : awsDate.getDate();
  var awsHours = (awsDate.getHours() < 10) ? '0' + awsDate.getHours() : awsDate.getHours();
  var awsMinutes = (awsDate.getMinutes() < 10) ? '0' + awsDate.getMinutes() : awsDate.getMinutes();
  var awsSeconds = (awsDate.getSeconds() < 10) ? '0' + awsDate.getSeconds() : awsDate.getSeconds();
  var awsOffsetFlag = (awsDate.getTimezoneOffset() == 0) ? 'Z' : ((awsDate.getTimezoneOffset() > 0) ? '-' : '+');
  var awsAbsoluteOffset = Math.abs(awsDate.getTimezoneOffset());
  var awsHoursOffset = awsOffsetFlag == 'Z' ? '' : ((awsAbsoluteOffset / 60) < 10) ? ('0' + parseInt(awsAbsoluteOffset / 60)) : (parseInt(awsAbsoluteOffset / 60));
  var awsMinutesOffset = awsOffsetFlag == 'Z' ? '' : ((awsAbsoluteOffset % 60) < 10) ? ('0' + parseInt(awsAbsoluteOffset % 60)) : (parseInt(awsAbsoluteOffset % 60));
  var awsString = awsYear + '-' + awsMonth + '-' + awsDay + 'T';
  awsString += awsHours + ':' + awsMinutes + ':' + awsSeconds + awsOffsetFlag + awsHoursOffset + awsMinutesOffset;
  return awsString;
}

awsIsoDateTime(new Date());

Timestamp UTC ISO 8601

function ISODateString(d) {
    function pad(n) {return n<10 ? '0'+n : n}
    return d.getUTCFullYear()+'-'
         + pad(d.getUTCMonth()+1)+'-'
         + pad(d.getUTCDate())+'T'
         + pad(d.getUTCHours())+':'
         + pad(d.getUTCMinutes())+':'
         + pad(d.getUTCSeconds())+'Z'
}

ISODateString(new Date());