Retrieve items from calender List only get first item

I am trying to get all items from my calender list i want to get EventDate and Enddate, here is my code,

function onQuerySucceeded() {

var startCon = listItemCustom + "T" + "08" + ":00" + "Z";
var endCon = listItemtoDate + "T" + "17" + ":00" + "Z";
var dtstartCon = new Date(startCon);
var dtEndCon = new Date(endCon);
var convertUtctoFromtime = new Date(dtstartCon.getTime() + dtstartCon.getTimezoneOffset() * 60 * 1000);
var start = new Date(convertUtctoFromtime);
var convertUtcToTime = new Date(dtEndCon.getTime() + dtEndCon.getTimezoneOffset() * 60 * 1000);
var end = new Date(convertUtcToTime);

var listItemEnumerator = collListItem.getEnumerator();
while (listItemEnumerator.moveNext()) {
    var oListItem = listItemEnumerator.get_current();
    while (end.getTime() >= start.getTime()) {

        var firstnewDate = (start.setTime(start.getTime()));
        var firstNewDt = new Date(firstnewDate);
        var newDate = start.setTime(start.getTime() + 30 * 60 * 1000);
        start = new Date(newDate);

        var eventDate = oListItem.get_item('EventDate');
        var endDate = oListItem.get_item('EndDate');

        var string = [[eventDate, endDate]];

            for (var i = 0; i < string.length; i++) {

                var date = string[i][0];
                var dt = new Date(date);

                var date2 = string[i][1];
                var dt2 = new Date(date2);


                 if (firstNewDt.getTime() != dt.getTime() && start.getTime() != dt2.getTime()) {
                     alert(firstNewDt + " " + start);
                 } else {

                     alert("Busy");

                 }
        }

    }
}

Right now i only get the first item from the list and displays alert("Busy") the second item that exists in the list wont display }