jquery 日期和时间的逻辑，比较大小

HTML:
<ul>
    <li>
        <span>到达</span>
        <img class="date-s" src="/public/test/img/date0.png" alt="" onclick="$('#date').focus();"
             data-field="datetime"/>
        <ul>
            <li class="time-s" data-date="start">9:00</li>
            <li class="time-e" data-date="start">2016.12.7</li>
        </ul>
    </li>
    <li>
        <span>出发</span>
        <img class="date-e" src="/public/test/img/date0.png" alt="" onclick="$('#date').focus();"
             data-field="datetime"/>
        <ul>
            <li class="time-s" data-date="end">21:00</li>
            <li class="time-e" data-date="end">2016.12.7</li>
        </ul>
    </li>
</ul>

JQery:
$('[name="desc"]').focus(function(){
    var s1= $(' ul li:first-child ul li:first-child').text();
    var s2=$(' ul li:last-child ul li:first-child').text();
    var a1=$(' ul li:first-child ul li:last-child').text();
    var start=new Date(a1.replace("-", "/").replace("-", "/"));
    var a2=$(' ul li:last-child ul li:last-child').text();
    var end=new Date(a2.replace("-", "/").replace("-", "/"));
    if(start>end){
       alert("日期选择有误");
        return false;
    }
    if((a1==a2)&&(s1>s2)){
        alert("时间选择有误");
        return false;
    }
   });