Can I change data before validate ?

I've date type

<xforms:bind name="control-13" nodeset="control-13" id="control-13-bind" type="xforms:date" />

In textbox type date value is 21/02/2555
I want to change value from 21/02/2555 to 21/02/2012 (change year only) and send value  to server for validate
But in client screen show 21/02/2555 in textbox

what should I do?