public function filterChangesOnly(array $oldValues, array &$newValues)
    {
        if ($newValues && $oldValues) {
            // \MUtil_Echo::track($newValues);
            // Remove up unchanged values
            foreach ($newValues as $name => $value) {
                if (array_key_exists($name, $oldValues)) {
                    /*
                     * Token->setValidFrom will convert to a string representation
                     * but values read from database will be Date objects. Make
                     * sure we compare string with strings
                     */
                    if ($value instanceof \Zend_Date) {
                        $value = $value->toString(\Gems_Tracker::DB_DATETIME_FORMAT);
                    }
                    if ($oldValues[$name] instanceof \Zend_Date) {
                        $oldValues[$name] = $oldValues[$name]->toString(\Gems_Tracker::DB_DATETIME_FORMAT);
                    }
                    // Extra condition for empty time in date values
                    if (($value === $oldValues[$name]) || ($value === $oldValues[$name] . ' 00:00:00')) {
                        unset($newValues[$name]);
                    }
                }
            }
        }

        return $newValues;
    }