Hello,
unfortunatelly the calendar module stores hardcoded strings like: YYYY-MM-DD instead of a timestamp. The latter one would allow to style the output in any way you like by the PHP function date.
A short fix for your problem is to extract month, date and year by the PHP function substr and to output the result in the order you want. Have a look to the file:
/modules/calendar/functions.php.
Around line 240 search for
echo $tmp['date_start'];
and replace it with
echo substr($tmp['date_start'],8,2) .'.' .substr($tmp['date_start'],5,2) .'.' .substr($tmp['date_start'],0,4);
Around line 256 search for
echo $tmp['date_end']." ";
and replace it with
echo substr($tmp['date_end'],8,2) .'.' .substr($tmp['date_end'],5,2) .'.' .substr($tmp['date_end'],0,4) .' ';
This allows you to style the output to whatever you need.
Regards Christian