issues

I have two netcdf datasets with the primary difference being the time resolution: one has data every minute, the other every 30 seconds. When I try to subset the 1-minute dataset with a time slice, it works fine, but when I do the same for the 30-second dataset it throws an error.

Two minimal netcdf files are in the attached, the one with "works" in the name has the 1-minute frequency and the other has the 30-second frequency. parcels.zip

What happened:

```python

ds = xr.open_dataset("parcel_example.nc") print(ds) ```

python <xarray.Dataset> Dimensions: (time: 293, yh: 1, zh: 1) Coordinates: xh float32 ... * yh (yh) float32 0.0 * zh (zh) float32 0.0 * time (time) timedelta64[ns] 00:00:00 00:00:30 ... 02:14:30 02:15:00 Data variables: (12/26) x (time) float32 ... y (time) float32 ... z (time) float32 ... u (time) float32 ... v (time) float32 ... w (time) float32 ... ... ...

```python print(ds.sel(time=slice("01:00:00","01:15:00")))

KeyError Traceback (most recent call last) ~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance) 3079 try: -> 3080 return self._engine.get_loc(casted_key) 3081 except KeyError as err:

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.DatetimeEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine._get_loc_duplicates()

pandas/_libs/index_class_helper.pxi in pandas._libs.index.Int64Engine._maybe_get_bool_indexer()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine._unpack_bool_indexer()

KeyError: 4559999999999

The above exception was the direct cause of the following exception:

KeyError Traceback (most recent call last) <ipython-input-16-c208cd704d0a> in <module> ----> 1 print(ds.sel(time=slice("01:00:00","01:15:00")))

~/miniconda3/envs/cm1/lib/python3.8/site-packages/xarray/core/dataset.py in sel(self, indexers, method, tolerance, drop, **indexers_kwargs) 2228 """ 2229 indexers = either_dict_or_kwargs(indexers, indexers_kwargs, "sel") -> 2230 pos_indexers, new_indexes = remap_label_indexers( 2231 self, indexers=indexers, method=method, tolerance=tolerance 2232 )

~/miniconda3/envs/cm1/lib/python3.8/site-packages/xarray/core/coordinates.py in remap_label_indexers(obj, indexers, method, tolerance, **indexers_kwargs) 414 } 415 --> 416 pos_indexers, new_indexes = indexing.remap_label_indexers( 417 obj, v_indexers, method=method, tolerance=tolerance 418 )

~/miniconda3/envs/cm1/lib/python3.8/site-packages/xarray/core/indexing.py in remap_label_indexers(data_obj, indexers, method, tolerance) 268 coords_dtype = data_obj.coords[dim].dtype 269 label = maybe_cast_to_coords_dtype(label, coords_dtype) --> 270 idxr, new_idx = convert_label_indexer(index, label, dim, method, tolerance) 271 pos_indexers[dim] = idxr 272 if new_idx is not None:

~/miniconda3/envs/cm1/lib/python3.8/site-packages/xarray/core/indexing.py in convert_label_indexer(index, label, index_name, method, tolerance) 119 "cannot use method argument if any indexers are slice objects" 120 ) --> 121 indexer = index.slice_indexer( 122 _sanitize_slice_element(label.start), 123 _sanitize_slice_element(label.stop),

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in slice_indexer(self, start, end, step, kind) 5275 slice(1, 3, None) 5276 """ -> 5277 start_slice, end_slice = self.slice_locs(start, end, step=step, kind=kind) 5278 5279 # return a slice

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in slice_locs(self, start, end, step, kind) 5480 end_slice = None 5481 if end is not None: -> 5482 end_slice = self.get_slice_bound(end, "right", kind) 5483 if end_slice is None: 5484 end_slice = len(self)

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_slice_bound(self, label, side, kind) 5394 except ValueError: 5395 # raise the original KeyError -> 5396 raise err 5397 5398 if isinstance(slc, np.ndarray):

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_slice_bound(self, label, side, kind) 5388 # we need to look up the label 5389 try: -> 5390 slc = self.get_loc(label) 5391 except KeyError as err: 5392 try:

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/timedeltas.py in get_loc(self, key, method, tolerance) 198 raise KeyError(key) from err 199 --> 200 return Index.get_loc(self, key, method, tolerance) 201 202 def _maybe_cast_slice_bound(self, label, side: str, kind):

~/miniconda3/envs/cm1/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance) 3080 return self._engine.get_loc(casted_key) 3081 except KeyError as err: -> 3082 raise KeyError(key) from err 3083 3084 if tolerance is not None:

KeyError: Timedelta('0 days 01:15:59.999999999')

```

What you expected to happen:

python ds = xr.open_dataset("parcel_example_works.nc") print(ds)

python <xarray.Dataset> Dimensions: (time: 136, yh: 1, zh: 1) Coordinates: xh float32 ... * yh (yh) float32 0.0 * zh (zh) float32 0.0 * time (time) timedelta64[ns] 00:00:00 00:01:00 ... 02:14:00 02:15:00 Data variables: (12/28) x (time) float32 ... y (time) float32 ... z (time) float32 ... u (time) float32 ... v (time) float32 ... w (time) float32 ... ... ...

```python print(ds.sel(time=slice("01:00:00","01:15:00")))

<xarray.Dataset> Dimensions: (time: 16, yh: 1, zh: 1) Coordinates: xh float32 1.0 * yh (yh) float32 0.0 * zh (zh) float32 0.0 * time (time) timedelta64[ns] 01:00:00 01:01:00 ... 01:14:00 01:15:00 Data variables: (12/28) x (time) float32 ... y (time) float32 ... z (time) float32 ... u (time) float32 ... v (time) float32 ... w (time) float32 ... ... ... b (time) float32 ... vpg (time) float32 ... zvort (time) float32 ... rho (time) float32 ... qsl (time) float32 ... qsi (time) float32 ... Attributes: CM1 version: cm1r20.1 Conventions: CF-1.7 missing_value: -999999.9 ```

Anything else we need to know?:

I can do what I need to do by using ds.where and other functions, so this isn't critical, but I thought I'd pass it along in case it is a broader issue. I at first thought it was the existing issue with timestamps highlighted in other issues like #4045, but I upgraded xarray and pandas and the problem still existed.

Environment: