Here is the formula in PHP language:

$start_date = strtotime(#תאריך יצירה#);
$end_date = strtotime(#תאריך שהפך ללקוח#);

if ($start_date && $end_date) {
$time_diff = $end_date – $start_date;
$average_time = round($time_diff / (60 * 60 * 24)); // Convert seconds to days
return “Average time: ” . $average_time . ” days”;
} else {
return “”; // Default empty value
}