CCalendarEvent::sortByDay

static function sortByDay(array $byDay)
{
	uasort($byDay, function($a, $b){
		$map = [
			'MO' => 0,
			'TU' => 1,
			'WE' => 2,
			'TH' => 3,
			'FR' => 4,
			'SA' => 5,
			'SU' => 6
		];

		return $map[$a] < $map[$b] ? -1 : 1;
	});

	return $byDay;
}