$availableValues = array();
$queryResult = array();
$sql = "SELECT DISTINCT date FROM letters_od_in_date WHERE user_id= '{$rowData['id']}'";
$this->GetConnection()->ExecQueryToArray($sql, $queryResult);
foreach ( $queryResult as $row) {
$date= $row['date'];
}
if ($fieldName == 'day') {
$udateOfBirth = new DateTime($date);
$dateInterval = $udateOfBirth->diff(new DateTime());
$value = $dateInterval->format('%d');
}