Get date value with jinput

Question

In my form I have selecting date with datetimepicker which i'm using only date picker.

I need to get the selected date value to do some calculation in php through ajax.
Here is my code but the result shows date starting 01/01/1970 !!

 public function getmydateHTML() {
     $jinput = JFactory::getApplication()->input;
     $db = JFactory::getDbo();
     $query = $db->getQuery(true);         
     $dt = $jinput->get ('dvalue');         
     $date = $jinput->get ('selectedate');
     $sdt = strtotime($date);
     $newdate = strtotime("+$dt day", $sdt);
     echo   date('d/m/Y', $newdate);      
    exit;  
}

How can I get correct selected date value?

Answer 1

Try to change it to:

"+$dt days"

Also, I may be wrong but, I believe you must provide dates in correct order as if dates diff is <0 then it would return 0 which corresponds to 01/01/1970