Wrong SelectedDate in DatePicker

i have datepicker this

<controls:datepicker fontsize="12" istodayhighlighted="true" height="20" width="150"

x:name="ddata" minwidth="150" firstdayofweek="monday" padding="0"

selecteddate="{binding ddata, mode=twoway, validatesonexceptions=true, notifyonvalidationerror=true}" />

also have domaindatasource like

<riacontrols:domaindatasource x:name="mydata" autoload="false" queryname="getnrcds" loadsize="20" >

<riacontrols:domaindatasource.domaincontext>

<ds:catalog />

</riacontrols:domaindatasource.domaincontext>

<riacontrols:domaindatasource.filterdescriptors>

<riadata:filterdescriptorcollection>

<riadata:filterdescriptor propertypath="nnr" operator="isequalto">

<riadata:controlparameter controlname="txtnr" propertyname="text" refresheventname="textchanged" />

</riadata:filterdescriptor>

</riadata:filterdescriptorcollection>

</riacontrols:domaindatasource.filterdescriptors>

</riacontrols:domaindatasource>

when bind data stapicker control shows data field - 1 day

any ideas ?

is ddata datetime?

Silverlight  >  WCF RIA Services with Silverlight