Date field update with XML-RPC API is not working

Date field update with XML-RPC API is not working

Hello
I am using XML-RPC API to update a date field in a form.
Although the return response is positive "Success" with new value of date field, when i viewing the record, nothing has been done
I am using the same API pour text or decimal fields and it works well
Can you confirm me, it is a bug or am I doing something wrong ?
Date value I am sending is '18-Feb-2008'
Thanks for your answer