Basho\Riak\TimeSeries\Cell::setDateTimeValue PHP Method

    public function setDateTimeValue($value = null)
    {
        if ($value != null && !$value instanceof \DateTime) {
            throw new \InvalidArgumentException('Expected a \\DateTime object.');
        }
        $this->type = Cell::TIMESTAMP_TYPE;
        $this->value = $value->getTimestamp();
        return $this;
    }