UNION之后日期被破坏

Question

我正在尝试UNION两个查询。这是我的代码：

public function ledger()
{
    $name = Input::get('client');

    $invoices = DB::table('invoices')
        ->where('client',$name)
        ->selectRaw('`invoiceNumber` as `voucher`,`date`,(`bill` + `ot_bill`) as `amount`');

    $cashIns = DB::table('cash_ins')
        ->where('client',$name)
        ->select('voucher','date','amount')
        ->unionAll($invoices)
        ->get();

    return view('cashIn.ledger',compact('cashIns'));
}

但是日期没有显示在表格中。当我查看dd($cashIns)时，所有日期都被破坏或格式不同。我不明白到底有什么回报。

array:3 [▼
  0 => {#301 ▼
    +"voucher": "JKL02390"
    +"date": b"ß\x07\f\x06"  //it suppose to be 2015-12-06
    +"amount": 23888
  }
  1 => {#304 ▼
    +"voucher": "KL8430"     //it suppose to be 2015-10-07
    +"date": b"""
      ß\x07\n
      \x07
      """
    +"amount": 98392
  }
  2 => {#305 ▼
    +"voucher": "433"
    +"date": b"ß\x07\f\x02"  //it suppose to be 2015-12-02
    +"amount": 9849
  }
]

当我单独dd('invoices')和dd('cashIns')没有UNION时，所有日期都格式正确并且完全显示为数据库。