function goLastMonth(month, year){
	if(month == 1){
		--year;
		month = 13;
	}
	document.location.href = 'calendar.php?month='+(month-1)+'&year='+year;
}

function goNextMonth(month, year){
	if(month == 12){
		++year;
		month = 0;
	}
	document.location.href = 'calendar.php?month='+(month+1)+'&year='+year;
}