I want to fill in some custom date fields via the API integration, the question is now how?

I do have the following XML-Tree:

$XMLDATA = '
<Accounts>
<row no="1">
<fieldlabel value="Account Name">TestUser</fieldlabel>
<fieldlabel value="Email">test@test.test</fieldlabel>
<fieldlabel value="boolean flag">TRUE</fieldlabel>
<fieldlabel value="First contact">01.01.2009</fieldlabel>
<fieldlabel value="Last Login">05.10.2009</fieldlabel>
</row>
</Accounts>';

The fields "First contact" and "Last Login" are date-fields.

The xml-Tree, see above, does not work. Do i have to use the following value "ACCOUNTCF81"?

Thank you for your help

Regards

Jan