OData Json "Value 2014-03-11T13:01:02Z does not represent a valid date/time"

Hi,

I'm trying to update a record in the new SAP demo System using OData and Json and receive errors.

The first error is "Value 2014-03-11T13:01:02Z does not represent a valid date/time" as response to the following request:

POST https://sapes4.sapdevcenter.com/sap/opu/odata/IWBEP/GWDEMO/ProductCollection HTTP/1.1
Cookie: SAP_SESSIONID_ES4_800=<SessionID>;
X-CSRF-Token: <CSRF-Token>
Content-Type: application/json; charset=utf-8
Host: sapes4.sapdevcenter.com
Expect: 100-continue
Content-Length: 693

{
  "ProductName": "Notebook Basic 15",
"ChangedAt": "2014-03-11T13:01:02Z",
  "TaxTariffText": null,
  "ProductID": "HT-1000",
  "DimensionUnit": null,
  "WeightUnitText": null,
  "UnitPrice": 95600.0,
  "ProductKey": "FF15FF203",
  "WeightMeasure": 0.0,
  "ProductWidth": 0.0,
  "DimensionUnitText": null,
  "SupplierID": null,
  "ProductDescription": null,
  "ProductCategory": null,
  "TaxTariffCode": 0,
  "QuantityUnit": null,
  "ProductTypeCode": null,
  "QuantityUnitText": null,
  "WeightUnitCode": null,
  "SupplierName": "0100000000",
  "CurrencyCode": null,
  "ProductHeight": 0.0,
  "CurrencyText": null,
  "ProductDepth": 0.0,
  "SupplierGuid": null
}

If I then play around with the date-format (for example omit the "Z" in the date string), I get "Error while parsing an XML stream" as response to the following request (note, that I'm using Json!):

POST https://sapes4.sapdevcenter.com/sap/opu/odata/IWBEP/GWDEMO/ProductCollection HTTP/1.1
Cookie: SAP_SESSIONID_ES4_800=7iFTONEanHtP4tr6RZtBvzOg-q3hMxHlvqwAUFaiFrg%3d;
X-CSRF-Token: Ha1u0NVPHG9DyEapG1vU8Q==
Content-Type: application/json; charset=utf-8
Host: sapes4.sapdevcenter.com
Expect: 100-continue
Content-Length: 692

{
  "ProductName": "Notebook Basic 15",
  "ChangedAt": "2014-03-11T13:01:02",
  "TaxTariffText": null,
  "ProductID": "HT-1000",
  "DimensionUnit": null,
  "WeightUnitText": null,
  "UnitPrice": 95600.0,
  "ProductKey": "FF15FF203",
  "WeightMeasure": 0.0,
  "ProductWidth": 0.0,
  "DimensionUnitText": null,
  "SupplierID": null,
  "ProductDescription": null,
  "ProductCategory": null,
  "TaxTariffCode": 0,
  "QuantityUnit": null,
  "ProductTypeCode": null,
  "QuantityUnitText": null,
  "WeightUnitCode": null,
  "SupplierName": "0100000000",
  "CurrencyCode": null,
  "ProductHeight": 0.0,
  "CurrencyText": null,
  "ProductDepth": 0.0,
  "SupplierGuid": null
}

Any ideas what's wrong here and how to solve it?

Thanks a lot

Michaela