function calculateDate() {
	var DAY_IN_MILIS = 1000*60*60*24;
	
	var dateDuration = document.getElementById('date_duration');
	var currentDate = new Date();
	
	//Data biezaca
	var y = currentDate.getFullYear();
	var m = currentDate.getMonth() + 1;
	var d = currentDate.getDate();
	if(d < 10) d = "0" + d;
	if(m < 10) m = "0" + m;
	
	var newDate = null;
	switch(parseInt(dateDuration[dateDuration.selectedIndex].value)) {
		case 0: newDate = new Date(currentDate - 7 * DAY_IN_MILIS); break;
		case 1: newDate = diffMonth(1); break;  
		case 2: newDate = diffMonth(3); break;
		case 3: newDate = diffMonth(6); break;
		case 4: newDate = diffMonth(12); break;
		case 5: newDate = diffMonth(18); break;
		case 6: newDate = diffMonth(24); break;
		case 7: newDate = diffMonth(36); break;
		default: return; break;
	}
	var sy = newDate.getFullYear();
	var sm = newDate.getMonth() + 1;
	var sd = newDate.getDate();
    if(sd < 10) sd = "0" + sd;
	if(sm < 10) sm = "0" + sm;
	
	document.getElementById('date_to').value = y + "-" + m + "-" + d;
	document.getElementById('date_from').value = sy + "-" + sm + "-" + sd;
}

function diffMonth(numOfMonths) {
	var currentDate = new Date();
	currentDate.setMonth(currentDate.getMonth() - numOfMonths);
	return currentDate;
}