エラーが起きてしまう

python3
1---------------------------------------------------------------------------
2ValueError                                Traceback (most recent call last)
3<ipython-input-7-4135c7fd37a7> in <module>
4     34     #     「日時」が2016-05-11～2017-05-10 → 2016-05-11、など
5     35     aligned = values.assign(
6---> 36         announcement_date=lambda x: pd.cut(
7     37             x['日時'],
8     38             (
9
10~\Anaconda3\lib\site-packages\pandas\core\frame.py in assign(self, **kwargs)
11   3652         if PY36:
12   3653             for k, v in kwargs.items():
13-> 3654                 data[k] = com.apply_if_callable(v, data)
14   3655         else:
15   3656             # <= 3.5: do all calculations first...
16
17~\Anaconda3\lib\site-packages\pandas\core\common.py in apply_if_callable(maybe_callable, obj, **kwargs)
18    363 
19    364     if callable(maybe_callable):
20--> 365         return maybe_callable(obj, **kwargs)
21    366 
22    367     return maybe_callable
23
24<ipython-input-7-4135c7fd37a7> in <lambda>(x)
25     40             ) + [np.datetime64(values['日時'].max() + pd.offsets.Day())],
26     41             labels=announcement_dates,
27---> 42             right=False
28     43         ).astype(
29     44             np.datetime64
30
31~\Anaconda3\lib\site-packages\pandas\core\reshape\tile.py in cut(x, bins, right, labels, retbins, precision, include_lowest, duplicates)
32    258         # GH 26045: cast to float64 to avoid an overflow
33    259         if (np.diff(bins.astype("float64")) < 0).any():
34--> 260             raise ValueError("bins must increase monotonically.")
35    261 
36    262     fac, bins = _bins_to_cuts(
37
38ValueError: bins must increase monotonically.