function getSeason() {
	var $date = new Date();
	var $day = $date.getDate();
	var $month = $date.getMonth() + 1;
	if (($month < 3) || ($month == 3 && $day < 20)) return 'zima';
	else if (($month < 6) || ($month == 6 && $day < 21)) return 'jaro';
	else if (($month < 9) || ($month == 9 && $day < 23)) return 'leto';
	else if (($month < 12) || ($month == 12 && $day < 21)) return 'podzim';
	else return 'zima';
}

function setStyleSheet($title) {
	var $i, $tag;
	if ($title == undefined) $title = getSeason();
	for ($i = 0; $tag = document.getElementsByTagName('link')[$i]; $i++) {
		if ($tag.rel.match('style') && ($tag.title != '')) {
			$tag.disabled = true;
			if ($tag.title == $title) $tag.disabled = false;
		}
	}
}

if (navigator.userAgent.indexOf('Safari/534') == -1) {
	setStyleSheet();
}