用jquery比较开始时间和结束时间？

这是代码

$(document).ready(function() {
    $('#st').change(function(){
        var st = $('#st').val(); // start time Format: '9:00 PM'
        var et = $('#et').val(); // end time   Format: '11:00 AM' 

        //how do i compare time
            if(st > et)
            {
               alert('end time always greater then start time');
            }
    });
});

如果我的时间范围如下

Start Time Range (listbox) =   12:00 AM To 11:59PM

End Time Range  (listbox)  =   12:00 AM To 11:59PM

那么如何验证开始时间小于结束时间或结束时间大于开始时间

Start-time < End-time  OR  End-time > St-time

考虑js代码中的时间格式，由于时间格式无法实现差异逻辑

Format: '9:00 AM'
Format: '5:00 PM'

这是我调查后得到的。
最佳实践如果时间格式 in 12小时制 Or 24小时制.

//start time
var start_time = $("#start_time").val();

//end time
var end_time = $("#end_time").val();

//convert both time into timestamp
var stt = new Date("November 13, 2013 " + start_time);
stt = stt.getTime();

var endt = new Date("November 13, 2013 " + end_time);
endt = endt.getTime();

//by this you can see time stamp value in console via firebug
console.log("Time1: "+ stt + " Time2: " + endt);

if(stt > endt) {
    $("#start_time").after('<span class="error"><br>Start-time must be smaller then End-time.</span>');
    $("#end_time").after('<span class="error"><br>End-time must be bigger then Start-time.</span>');
        return false;
}