[AndrewGSW]

Something like:

var i = 0, d, xmlBodyN, xmlCreate, newCreate, jsDate;

while (d = document.getElementById("Body" + i)) {
    xmlBodyN = xmlDoc.getElementsByTagName("Body")[i];
    if (xmlBodyN) {
        d.innerHTML = xmlBodyN.childNodes[0].nodeValue;
        xmlCreate = xmlDoc.getElementsByTagName("Created")[i];
        if (!xmlCreate) continue;
        newCreate = document.createElement('span');
        newCreate.id = "Timestamp" + (i++);
        d.parent.insertBefore(newCreate, d);

        xmlCreate = xmlCreate.childNodes[0].nodeValue;
        jsDate = new Date(xmlCreate);
        jsDate = jsDate.format('mmmm dxx, h:nnap');
        newCreate.innerHTML = jsDate;
    } else {
        break;
    }
}

but if this code makes no sense, and/or you are unable to incorporate it, then you may need to employ someone to do this for you.

Change "Timestamp" to "Created" if you want the new spans named "Created0", "Created1", etc..