Remind::getSpecificTime

public function getSpecificTime(): Date
{
	if (
		$this->specificTime === null
		&& $this->time !== null
		&& $this->units
		&& $this->eventStart !== null
	)
	{
		return (clone $this->eventStart)->sub("{$this->time} {$this->units}");
	}

	if ($this->specificTime)
	{
		return $this->specificTime;
	}

	throw new PropertyException('It is impossible to perform this operation. You should set property $eventStart or $specificTime');
}