function switchbg()
{
	var today = new Date();
	var hours = today.getHours();
	var month = today.getMonth() + 1;
	var b;
	if (hours > 17 || hours < 9)
	{
		b = document.getElementById("changebg");
		if (b) b.className = "switchbg1";
	}
	else  if (month < 3 || month > 11)
	{
		b = document.getElementById("changebg");
		if (b) b.className = "switchbg2";
	}
	else
	{
		b = document.getElementById("changebg");
		if (b) b.className = "switchbg3";
	}
}