function set_interval(period_from, period_to, period) {
	$A(period.options).each(function(o){o.remove();});
	var opts = [['5 minutes', 1], ['30 minutes', 2], ['1 hour', 3], ['2 hours', 4], ['1 day', 5], ['1 week', 6], ['1 month', 7], ['1 quarter', 8], ['1 year', 9], ['intraday (login)', 10]];
	var p1 = $D(period_from);
	var p2 = $D(period_to);
	var options;
	var interval = (p2-p1)/1000/60; // minutes
	// alert(interval);
	if (interval < 5){ // 5 min
		    alert('Period must be higher than 5 minutes');
		    options = [];
		} else if (interval >= 5 && interval < 30){ // 5 min and 30 min
		    options = opts.slice(0,1);
		} else if (interval >= 30 && interval < 60){ // 30 min and 60 min
		    options = opts.slice(0,2);
		} else if (interval >= 60 && interval < 120){ // 1 hour and 2 hours
		    options = opts.slice(0,3);
		} else if (interval >= 120 && interval < 1440){ // 2 hours and day
		    options = opts.slice(1,4);
		} else if (interval >= 1440 && interval < 10080){ // day and week
		    options = opts.slice(3,5);
		} else if (interval >= 10080 && interval < 43200){ // week and month
		    options = opts.slice(4,6);
		} else if (interval >= 43200 && interval < 129600){ // month and quarter
		    options = opts.slice(4,7);
		} else if (interval >= 129600 && interval < 388800){ // quarter and year
		    options = opts.slice(5,8);
		} else if (interval >= 388800){ // more than a year
		    options = opts.slice(6,9);
		} else {
		    options = [];
		}
		
	period_param = get_url_param('period')
	
	options.reverse().each(function(o_values){
			
			if (o_values[1] == period_param) {
		  	o = new Option(o_values[0], o_values[1], true);
		  } else {
		  	o = new Option(o_values[0], o_values[1]);
		  }

			period.options.add(o, 0);
		})
};
//Date.daysInMonth(p1.getFullYear(), p1.getMonthNumber())
//set_interval($('period_from').value, $('period_to').value, $('period'));

function get_url_param(name){
  name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
  var regexS = "[\\?&]"+name+"=([^&#]*)";
  var regex = new RegExp( regexS );
  var results = regex.exec( window.location.href );
  if( results == null )
    return "";
  else
    return results[1];
}