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
928381010,MDU6SXNzdWU5MjgzODEwMTA=,5515,NetCDF: Attempting netcdf-4 operation on netcdf-3 file,20254164,open,0,,,4,2021-06-23T15:23:55Z,2023-03-27T21:07:32Z,,CONTRIBUTOR,,,,"I'm trying to open MODIS .hdf files, but I get the error : `NetCDF: Attempting netcdf-4 operation on netcdf-3 file`. Does anyone knows how to open that files? (https://nsidc.org/data/MOD10C1)

```python
import xarray as xr
xr.open_dataset('MOD10C1.A2000055.061.2020037182124.hdf')

RuntimeError: NetCDF: Attempting netcdf-4 operation on netcdf-3 file
```


I already opened hdf files from another product without any issue... (https://nsidc.org/data/MOD10CM)

Here are two examples, with one that works and the other one that causes the issue: [MODIS.zip](https://github.com/pydata/xarray/files/6703060/MODIS.zip)

Thanks in advance for your help!


<details><summary>Output of <tt>xr.show_versions()</tt></summary>



<!-- Paste the output here xr.show_versions() here -->
INSTALLED VERSIONS
------------------
commit: None
python: 3.8.5 | packaged by conda-forge | (default, Jul 24 2020, 01:25:15) 
[GCC 7.5.0]
python-bits: 64
OS: Linux
OS-release: 4.19.0-16-amd64
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: fr_FR.UTF-8
LOCALE: fr_FR.UTF-8
libhdf5: 1.10.6
libnetcdf: 4.7.4

xarray: 0.16.0
pandas: 1.1.0
numpy: 1.19.1
scipy: 1.5.2
netCDF4: 1.5.4
pydap: None
h5netcdf: None
h5py: None
Nio: None
zarr: 2.4.0
cftime: 1.2.1
nc_time_axis: 1.2.0
PseudoNetCDF: None
rasterio: 1.1.5
cfgrib: 0.9.8.5
iris: None
bottleneck: None
dask: 2.21.0
distributed: 2.21.0
matplotlib: 3.2.0
cartopy: 0.17.0
seaborn: None
numbagg: None
pint: None
setuptools: 49.2.0.post20200712
pip: 20.2
conda: None
pytest: 6.0.0
IPython: 7.16.1
sphinx: None

</details>
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514529201,MDExOlB1bGxSZXF1ZXN0MzM0MTMxMzI1,3464,Error in leap year?,20254164,closed,0,,,13,2019-10-30T09:54:07Z,2019-10-31T13:15:16Z,2019-10-30T14:51:40Z,CONTRIBUTOR,,0,pydata/xarray/pulls/3464,"I've tried this script; however, it adds +1 to all months of the leap years. It sounds like an error, or I am wrong? So I wrote the condition ""and month == 2"" line 86 so that only the month of February gets +1.

<!-- Feel free to remove check-list items aren't relevant to your change -->

 - [ ] Closes #xxxx
 - [ ] Tests added
 - [ ] Passes `black . && mypy . && flake8`
 - [ ] Fully documented, including `whats-new.rst` for all changes and `api.rst` for new API
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3464/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
514539931,MDU6SXNzdWU1MTQ1Mzk5MzE=,3465,Error in xarray/doc/examples/monthly-means.rst line 86 ?,20254164,closed,0,,,0,2019-10-30T10:10:22Z,2019-10-30T14:51:54Z,2019-10-30T14:51:54Z,CONTRIBUTOR,,,,"I have made a pull request (Error in leap year? #3464) but I don't know how it works.
I guess there is a mistake in xarray/doc/examples/monthly-means.rst line 86 : 

I've tried this script; however, it adds +1 to all months of the leap years. It sounds like an error, or I am wrong? So I wrote the condition ""and month == 2"" line 86 so that only the month of February gets +1.

So I propose :
> if leap_year(year, calendar=calendar) and month == 2:

Instead of:
> if leap_year(year, calendar=calendar):


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