* @param string $query The XPath query of the nodes to return
* @param bool|null $multi Whether to return multiple results as an array (true) or one result as a date object (false, default)
* @param bool|null $mode Whether to return the first valid date found (DATE_ANY), the earliest chronologically (DATE_EARLIEST), latest chronologically (DATE_LATEST), or all valid dates (DAATE_ALL) in a sorted array
* @param \DOMNode $context The context node for the XPath query
/** Fetches the schedule interval from an RSS feed; this is necessarily approximate:
*
* The interval is defined in the syndication RSS extension as fractions of a period, but PHP only supports integer intervals, so we perform integer divison on the nearest subdivision of a period, returning at least one.
*
* For example, "four times monthly" first assumes a month is 30 days, and divides this by four to yield seven days.
*/
protected function getSchedIntervalRss1(): ?\DateInterval {