diff --git a/lib/db.coffee b/lib/db.coffee
index b008426..cb7aa80 100644
--- a/lib/db.coffee
+++ b/lib/db.coffee
@@ -407,7 +407,7 @@ saveDevice = (deviceId, deviceData, isNew, callback) ->
             switch attrName
               when 'value'
                 if not diff[1] or diff[2].value[1][0] != diff[1].value?[1][0]
-                  if diff[2].value[1][1] == 'xsd:dateTime'
+                  if diff[2].value[1][1] == 'xsd:dateTime' and Number.isInteger(diff[2].value[1][0])
                     update['$set'][path.concat('_value').join('.')] = new Date(diff[2].value[1][0])
                   else
                     update['$set'][path.concat('_value').join('.')] = diff[2].value[1][0]
diff --git a/lib/device.js b/lib/device.js
index eac1400..5967a7d 100644
--- a/lib/device.js
+++ b/lib/device.js
@@ -49,12 +49,13 @@ function sanitizeParameterValue(parameterValue) {
         break;
       case 'xsd:dateTime':
         if (typeof parameterValue[0] !== 'number') {
-          if (parameterValue[0].getTime() != null)
-            parameterValue[0] = parameterValue[0].getTime();
-          else if (isNaN(parameterValue[0]))
-            parameterValue[0] = Date.parse(parameterValue[0]);
-          else
-            parameterValue[0] = +parameterValue[0];
+          let v = +parameterValue[0];
+          if (isNaN(v)) {
+            v = Date.parse(parameterValue[0]);
+            if (isNaN(v))
+              v = '' + parameterValue[0];
+          }
+          parameterValue[0] = v;
         }
         break;
       default:
diff --git a/lib/soap.js b/lib/soap.js
index 040f4d1..5e6b1f9 100644
--- a/lib/soap.js
+++ b/lib/soap.js
@@ -210,7 +210,10 @@ function SetParameterValues(xml, methodRequest) {
   for (const p of methodRequest.parameterList) {
     const pvs = paramList.node("ParameterValueStruct");
     pvs.node("Name").text(p[0]);
-    pvs.node("Value").attr({"xsi:type": p[2]}).text(p[1]);
+    if (p[2] === 'xsd:dateTime' && Number.isInteger(p[1]))
+      pvs.node("Value").attr({"xsi:type": p[2]}).text((new Date(p[1])).toISOString());
+    else
+      pvs.node("Value").attr({"xsi:type": p[2]}).text(p[1]);
   }
 
   el.node("ParameterKey").text(methodRequest.parameterKey || "");