<form>
<input type="text" maxlength="2" name="day" />/
<input type="text" maxlength="2" name="month" />/
<input type="text" maxlength="4" name="year" onblur="this.form.date.value=this.form.day.value+'/'+this.form.month.value+'/'+this.form.year.value" />
<input type="hidden" name="date" />
</form>