bootstrap布局两列或者多列表单

<div class="form-group">
<label for="starttime" class="col-sm-2 control-label">实际开始时间</label>
<div class="col-md-4">
<input class="form-control" type="text" id="starttime" readonly="readonly" onchange="checkNull(this,'submitButton')" />
</div>
<label for="endtime" class="col-sm-2 control-label">实际结束时间</label>
<div class="col-md-4">
<input class="form-control" type="text" id="endtime" readonly="readonly" onchange="checkNull(this,'submitButton')" />
</div>
</div>