public function addTag($tag)
    {
        $this->tags[] = (string)$tag;
        $this->ref = null;
        return $this;
    }
public function addTag($tag)
    {
        $this->tags[] = (string)$tag;
        $this->ref = null;
        return $this;
    }
public function addTag ( $ tag ) { $ this -> tags [ ] = ( string ) $ tag ; $ this -> ref = null ; return $ this ; }
Adds another tag to the TimePoint
@param string $tag
@return TimePoint
Adds another tag to the TimePoint