Page Load fires twice on every first time pageload using updatepanel

You have to bind the datepicker to the text box in the ready function.

<script type="text/javascript">
    $(document).ready(function () {
        $('#<%=TxtTo.ClientID%>').datepicker({
            changeMonth: true,
            changeYear: true,
            yearRange: '-5:+0',
            duration: 'fast',
            dateFormat: 'dd-M-yy',
            showAnim: 'slideDown',
            maxDate: '0'
        });
    });
</script>