CX_SY_CONVERSION_NO_DATE_TIME:XSLT exception when calling Web Service

I have created a web service for the standard Function Module SAP_WAPI_CREATE_WORKLIST. The function module executes successfully through SE37.

When I test the web service using the Logical Port and the Proxy created I get the following error.

"CX_SY_CONVERSION_NO_DATE_TIME:XSLT exception when calling Web Service"

I have also created a ZSAP_WAPI_CREATE_WORKLIST wrapper function module to see if I can modify the date time conversion but in vain.

Please advice as to how should I avoid this error.