日期输入D-M-Y在数据库中搜索之前转换为Y-M-D

In my database date is saved as Y-M-D in the Date format. But I dont want to input in that way. Is it possible to convert D-M-Y before searching in database? In my code the input form get the date of today.

Code:

HTML

  <form name="input" action="" method="POST">
  Fra Dato: <input type="text" name="fraDato" value="<?php echo date('Y-m-d'); ?>" /> <br>
Til Dato: <input type="text" name="tilDato" value="<?php echo date('Y-m-d'); ?>"> <br> 
<input type="submit" name="submit" value="Visualiser" > <br>
  <input type="checkbox" id="PH" value="PH" >PH<br>
<input type="checkbox" id="Chlorine" value="Chlorine" >Chlorine<br>
<input type="checkbox" id="Temperature" value="Temperature" >Temperature<br> 

</form> 

PHP:

<?php
  $timezone = "Europe/Oslo";
  date_default_timezone_set($timezone);



if(isset($_POST['submit']))
{

$fraDato=$_REQUEST['fraDato'];
$tilDato=$_REQUEST['tilDato'];



$con=mysql_connect("localhost","root","") or die("Failed to connect with database!!!!");
mysql_select_db("chart", $con);

$sth = mysql_query("SELECT PH, Chlorine, Temperature, Date, Time FROM googlechart where Date between '".$fraDato."' and '".$tilDato."' order by Date, Time");

?>

Yes you can concert dates easily with DateTime::createFromFormat,

$date = DateTime::createFromFormat('d-m-Y', $_REQUEST['fraDato']);
echo $fraDato = $date->format('Y-m-d');