uesless tag 'rc-time-picker-icon' ?

[hua-lu]

<span class="rc-time-picker ">  
   <input type="text" class="rc-time-picker-input" value="">  
   <span class="rc-time-picker-icon"></span>  
</span>  

Could someone explain what this span with class 'rc-time-picker-icon' is for ?