jquery 日期和時間的邏輯，比較大小

HTML:
<ul>
 <li>
 <span>到達</span>
 <img class="date-s" src="/public/test/img/date0.png" alt="" onclick="$('#date').focus();"
 data-field="datetime"/>
 <ul>
 <li class="time-s" data-date="start">9:00</li>
 <li class="time-e" data-date="start">2016.12.7</li>
 </ul>
 </li>
 <li>
 <span>出發</span>
 <img class="date-e" src="/public/test/img/date0.png" alt="" onclick="$('#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("日期選擇有誤");
 return false;
 }
 if((a1==a2)&&(s1>s2)){
 alert("時間選擇有誤");
 return false;
 }
 });