how to change date format in web service request menu

It s proably too simple but I dont have any clue . My problem is I have a web service which is invoked by adobe invoke web service process.

and I have FormData which is xml and input .

FormData contains a few information  such as 

<FormData>

<Field01MusteriNo>123456</Field01MusteriNo>
    <StartDate>25/01/2010</StartDate>
    <EndDate>30/06/2012</EndDate>
</FormData>

However My Web Service requires the dates such as yyyy-mm-dd type

   <soapenv:Body>
      <core:SelectNotFinishedDifferenceDocumentList>
         <core:customerNumber>123456</core:customerNumber>
         <core:startDate>2010-01-25</core:startDate>
         <core:endDate>2010-06-30</core:endDate>
      </core:SelectNotFinishedDifferenceDocumentList>
   </soapenv:Body>

so it s simply  how to convert 25/01/2010 (dd/mm/yyyy) to 2010-01-25 (yyyy-mm-dd) in web service request menu

I already try to put T00:00:00 end of date it didnt work