WdatePicker设置时间区间时，对开始时间和结束时间限制

<input id="startDate" name="startDate"  type="text" readonly="readonly" maxlength="20" class="input-small Wdate" onFocus="WdatePicker({dateFmt:'yyyy-MM-dd HH:mm:ss',maxDate:'#F{$dp.$D(\'endDate\')}'})"/>
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        <input id="endDate" name="endDate" type="text" readonly="readonly" maxlength="20" class="input-small Wdate" onFocus="WdatePicker({dateFmt:'yyyy-MM-dd HH:mm:ss',minDate:'#F{$dp.$D(\'startDate\')}'})"/>