public function toDecimal() : string
    {
        $result = (string) $this->epochSecond;

        if ($this->nano !== 0) {
            $nano = (string) $this->nano;
            $nano = str_pad($nano, 9, '0', STR_PAD_LEFT);
            $nano = rtrim($nano, '0');

            $result .= '.' . $nano;
        }

        return $result;
    }