What happened?

When I try to select a subset of the data in a dataset/array with a list containing dates it fails when the time index is in cftime, and I get the following error message:

KeyError: "not all values found in index 'time'"

What did you expect to happen?

I expect selecting a set of dates with a list to work the same way as when the time index is in datetime64.

Minimal Complete Verifiable Example

```Python import xarray as xr import numpy as np

ds = xr.open_dataset("https://thredds.met.no/thredds/dodsC/osisaf/met.no/ice/index/v2p1/nh/osisaf_nh_sie_daily.nc")

Time coordinates are in datetime64, and selecting dates with a list works.

print(ds.time) print(ds.sel(time=["2023-01-01", "2023-01-02"]))

Converting the calendar to all_leap changes the time coordinates to use cftime instead of datetime64.

ds = ds.convert_calendar("all_leap", missing=np.nan).interpolate_na()

Time coordinates are in cftime, and selecting dates with a list fails.

print(ds.time) print(ds.sel(time=["2023-01-01", "2023-01-02"])) ```

MVCE confirmation

• [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [X] Complete example — the example is self-contained, including all data and the text of any traceback.
• [X] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [X] New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

Python (geoscience) [michael@localhost ~]$ python minimal.py <xarray.DataArray 'time' (time: 16107)> array(['1979-01-01T00:00:00.000000000', '1979-01-02T00:00:00.000000000', '1979-01-03T00:00:00.000000000', ..., '2023-02-03T00:00:00.000000000', '2023-02-04T00:00:00.000000000', '2023-02-05T00:00:00.000000000'], dtype='datetime64[ns]') Coordinates: * time (time) datetime64[ns] 1979-01-01 1979-01-02 ... 2023-02-05 sic_threshold float32 ... lat float32 ... lon float32 ... Attributes: standard_name: time long_name: time of the observation (centered) coverage_content_type: auxiliaryInformation axis: T <xarray.Dataset> Dimensions: (time: 2, nv: 2) Coordinates: * time (time) datetime64[ns] 2023-01-01 2023-01-02 sic_threshold float32 ... lat float32 ... lon float32 ... Dimensions without coordinates: nv Data variables: lat_bounds (nv) float32 ... lon_bounds (nv) float32 ... area |S64 ... sie (time) float64 ... source (time) float64 ... Attributes: (12/35) title: Daily Northern Hemisphere Sea Ice Extent from EU... product_id: OSI-420 product_name: OSI SAF Sea Ice Index product_status: demonstration version: v2p1 summary: Time series of Daily Sea Ice Extent (SIE) for No... ... ... distribution_statement: Free copyright_statement: Copyright 2023 EUMETSAT references: Product User Manual for OSI-420, Lavergne et al.... featureType: timeSeries DODS.strlen: 2 DODS.dimName: nchar <xarray.DataArray 'time' (time: 16140)> array([cftime.DatetimeAllLeap(1979, 1, 1, 0, 0, 0, 0, has_year_zero=True), cftime.DatetimeAllLeap(1979, 1, 2, 0, 0, 0, 0, has_year_zero=True), cftime.DatetimeAllLeap(1979, 1, 3, 0, 0, 0, 0, has_year_zero=True), ..., cftime.DatetimeAllLeap(2023, 2, 3, 0, 0, 0, 0, has_year_zero=True), cftime.DatetimeAllLeap(2023, 2, 4, 0, 0, 0, 0, has_year_zero=True), cftime.DatetimeAllLeap(2023, 2, 5, 0, 0, 0, 0, has_year_zero=True)], dtype=object) Coordinates: * time (time) object 1979-01-01 00:00:00 ... 2023-02-05 00:00:00 lat float32 90.0 lon float32 0.0 sic_threshold float32 0.15 Attributes: standard_name: time long_name: time of the observation (centered) coverage_content_type: auxiliaryInformation axis: T Traceback (most recent call last): File "/var/home/michael/minimal.py", line 15, in <module> print(ds.sel(time=["2023-01-01", "2023-01-02"])) File "/var/home/michael/mambaforge/envs/geoscience/lib/python3.10/site-packages/xarray/core/dataset.py", line 2554, in sel query_results = map_index_queries( File "/var/home/michael/mambaforge/envs/geoscience/lib/python3.10/site-packages/xarray/core/indexing.py", line 183, in map_index_queries results.append(index.sel(labels, **options)) # type: ignore[call-arg] File "/var/home/michael/mambaforge/envs/geoscience/lib/python3.10/site-packages/xarray/core/indexes.py", line 480, in sel raise KeyError(f"not all values found in index {coord_name!r}") KeyError: "not all values found in index 'time'"

Anything else we need to know?

No response

Environment

/var/home/michael/mambaforge/envs/geoscience/lib/python3.10/site-packages/_distutils_hack/__init__.py:33: UserWarning: Setuptools is replacing distutils. warnings.warn("Setuptools is replacing distutils.") INSTALLED VERSIONS ------------------ commit: None python: 3.10.9 | packaged by conda-forge | (main, Feb 2 2023, 20:20:04) [GCC 11.3.0] python-bits: 64 OS: Linux OS-release: 6.1.9-200.fc37.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: ('en_GB', 'UTF-8') libhdf5: 1.12.2 libnetcdf: 4.8.1 xarray: 2022.11.0 pandas: 1.5.1 numpy: 1.23.4 scipy: 1.9.3 netCDF4: 1.6.1 pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.6.2 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: 1.3.6 dask: None distributed: None matplotlib: 3.6.2 cartopy: 0.21.0 seaborn: 0.12.1 numbagg: None fsspec: None cupy: None pint: None sparse: None flox: None numpy_groupies: None setuptools: 65.5.1 pip: 22.3.1 conda: None pytest: None IPython: 8.6.0 sphinx: None