issues: 1970215879

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1970215879 PR_kwDOAMm_X85eOCcn 8393 Port fix from pandas-dev/pandas#55283 to cftime resample 6628425 closed 0     1 2023-10-31T11:12:09Z 2023-11-02T09:40:46Z 2023-11-02T04:12:51Z MEMBER   0 pydata/xarray/pulls/8393

The remaining failing cftime resample tests in https://github.com/pydata/xarray/issues/8091 happen to be related to a bug that was fixed in the pandas implementation, https://github.com/pandas-dev/pandas/pull/55283, leading answers to change in some circumstances. This PR ports that bug fix to xarray's implementation of resample for data indexed by a CFTimeIndex.

A simple example where answers change in pandas is the following:

Previously

```

import numpy as np; import pandas as pd index = pd.date_range("2000", periods=5, freq="5D") series = pd.Series(np.arange(index.size), index=index) series.resample("2D", closed="right", label="right", offset="1s").mean() 2000-01-01 00:00:01 0.0 2000-01-03 00:00:01 NaN 2000-01-05 00:00:01 1.0 2000-01-07 00:00:01 NaN 2000-01-09 00:00:01 NaN 2000-01-11 00:00:01 2.0 2000-01-13 00:00:01 NaN 2000-01-15 00:00:01 3.0 2000-01-17 00:00:01 NaN 2000-01-19 00:00:01 NaN 2000-01-21 00:00:01 4.0 Freq: 2D, dtype: float64 ```

Currently

```

import numpy as np; import pandas as pd index = pd.date_range("2000", periods=5, freq="5D") series = pd.Series(np.arange(index.size), index=index) series.resample("2D", closed="right", label="right", offset="1s").mean() 2000-01-01 00:00:01 0.0 2000-01-03 00:00:01 NaN 2000-01-05 00:00:01 NaN 2000-01-07 00:00:01 1.0 2000-01-09 00:00:01 NaN 2000-01-11 00:00:01 2.0 2000-01-13 00:00:01 NaN 2000-01-15 00:00:01 NaN 2000-01-17 00:00:01 3.0 2000-01-19 00:00:01 NaN 2000-01-21 00:00:01 4.0 Freq: 2D, dtype: float64 ```

This PR allows us to reproduce this change in xarray for data indexed by a CFTimeIndex. The bin edges were incorrect in the previous case; see https://github.com/pandas-dev/pandas/pull/52064#issuecomment-1785893752 for @MarcoGorelli's nice explanation as to why.

 
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