private static function expandDaysRange(array $days) : array
	{
		static $dayNames = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun',];
		$expandedValues = [];

		foreach ($days as $day) {
			if (Strings::match($day, '~^\w{3}\s*-\s*\w{3}$~u')) {
				list($begin, $end) = Strings::split($day, '~\s*-\s*~');
				$started = FALSE;
				foreach ($dayNames as $dayName) {
					if ($dayName === $begin) {
						$started = TRUE;
					}
					if ($started) {
						$expandedValues[] = $dayName;
					}
					if ($dayName === $end) {
						$started = FALSE;
					}
				}
			} else {
				$expandedValues[] = $day;
			}
		}

		return array_unique($expandedValues);
	}