更改datepicker后连续更新日期字段

I have a table that contains a column of dates that can be changed through the datepicker .

<td>
   <div class="input-group date" data-provide="datepicker">
        <input type="text" class="form-control" name="dataPrevisao" id="dataPrevisao" rel="<?php echo odbc_result($resultado,"stamp");?>" value="<?php echo odbc_result($resultado,"dvalor");?>" />
        <div class="input-group-addon">
             <span class="glyphicon glyphicon-calendar small"></span>
        </div>
   </div>

What i want to do, is after the change of date, the register is automatically updated in the table. For that, i have a php file - changePrevisao.php:

<?php include("includes/odbc.ini"); 
$iniciais=str_replace(' ', '', $_SESSION['iniciais']);
$stamp=$_POST['stamp']; 
$dataP=$_POST['dataP']; 
$query = "  update od set marcada=1, data='$dataP', usrdata=convert(varchar(10),getdate(),112),
            usrhora=right(convert(varchar(19),getdate(),121),8), usrinis='$iniciais' where od.odstamp='$stamp'";
odbc_exec($sqlconnect,$query); 
?>

I have problems in building the user function to ajax that allows pass the data to the php file , does anyone can help me ?

After searching and testing , I created the following function:

<script>
    $(document).ready(function(){
    $(document).on('change', '#dataPrevisao', function () {
        var stamp = $(this).attr('rel');
        var dataP = $(this).val();
        var dataString = 'stamp='+ stamp +'&dataP='+ dataP;
        $.ajax({
            type: "POST",
            url: "changePrevisao.php",
            data: dataString,
            cache: false,
            success: function(new_data){
                    $(stamp).html(new_data);
                    $(stamp).dialog();
                    alert('Load was performed.');
    }
   });
  });
});
</script>

Now i can update the date in the db, but the result is not as i expected, the change only occurs when I change directely the input and not through the datepicker. What do I need to change in the function so that it takes into account the changes made by the datepicker ?