public function setDateActivation($dateActivation)
    {
        $dateActivation = ($dateActivation === null ? $dateActivation : (string) $dateActivation);

        if ($this->exists() && $this->dateActivation !== $dateActivation) {
            $this->updated['dateActivation'] = true;
        }

        $this->dateActivation = $dateActivation;

        return $this;
    }