function linkToYesterday(){
		date = new Date();
		date.setTime((new Date()).getTime()-86400000);
		
		year = date.getYear();
		if (year < 2000) year += 1900;
		month = date.getMonth()+1;
		if(month<10){
			month = "0" + month;
		}
		yesterday = date.getDate();
		if(yesterday<10){
			yesterday = "0" + yesterday;
		}
		
		document.write('<a href="http://ringoon.jp/'+year+'/'+month+'/'+yesterday+'/">');
		document.write('&laquo; '+year+'年'+month+'月'+yesterday+'日</a>');
	}

	function tweet() {
		bitly = 'http://ringoon.jp/bitly/proxy.php?version=2.0.1&format=json&callback=callback&longUrl=';
		var script = document.createElement('script');
		script.type = 'text/javascript';
		script.src = bitly + encodeURIComponent(location.href) ;
		document.body.appendChild(script);
	}