JSFiddle - React, Tailwind, and code Playground

JavaScript

function calenDate(icalStr)  {
    // icalStr = '20110914T184000Z'             
    var strYear = icalStr.substr(0,4);
    var strMonth = parseInt(icalStr.substr(4,2),10) - 1;
    var strDay = icalStr.substr(6,2);
    var strHour = icalStr.substr(9,2);
    var strMin = icalStr.substr(11,2);
    var strSec = icalStr.substr(13,2);

    var oDate =  new Date(strYear,strMonth, strDay, strHour, strMin, strSec)

return oDate;
}


var strData = 'DTSTART:20110914T184000Z'
var x = strData.indexOf(":");
var strVal = strData.slice(x + 1 );
var dateObj = calenDate(strVal);
document.write(dateObj);