interface DateTimeInterface

interface DateTimeInterface {
    
    /**
     * Returns the date time object.
     *
     * @return \Drupal\Core\Datetime\DrupalDateTime|null
     *   A date object or NULL if there is no date.
     */
    public function getDateTime();
    
    /**
     * Sets the date time object.
     *
     * @param \Drupal\Core\Datetime\DrupalDateTime $dateTime
     *   An instance of a date time object.
     */
    public function setDateTime(DrupalDateTime $dateTime);

}