[S2] Date Validation

[Rodrigo Pereira]

Hi,
how can I validate a datetime picker?

I have the following in my validation.xml file:
<field name="date">


<field-validator type="required">

<message key="errors.date.required"/>

</field-validator>


</field>

but I am getting this error message:
05/04/2008 14:53:41 org.apache.struts2.components.DateTimePicker format

SEVERE: Could not parse date

java.text.ParseException: Unparseable date: ""

If I comment this field validation, all the rest of my validation on this form 
work.

Does anybody have an idea what I am doing wrong?

Thanks,
Rodrigo Pereira