issue_comments: 610466323

unfortunately, numpy does not allow us to put cftime object into dtypes (yet!), so ds.time.values is a numpy.ndarray with dtype object, containing cftime objects. To make the code work, use it with ds.time.values[0]. Of course, that won't help if the array contains objects of more than one type.

```python

import cftime isinstance(ds.time.values[0], cftime.DatetimeNoLeap) True type(ds.time.values[0]) <class 'cftime._cftime.DatetimeNoLeap'> I use the following, which seems to work for me but I thought something shorter and more elegant could be done ... def get_time_date_type(ds: Union[xr.Dataset, xr.DataArray]):

if ds.time.dtype == "O":
    if len(ds.time.shape) == 0:
        time0 = ds.time.item()
    else:
        time0 = ds.time[0].item()
    return type(time0)
else:
    return np.datetime64

```

In #3498, the original proposal was to name the new kwarg master_file, but later it was renamed to attrs_file. If l_f is a list of file paths, you used it correctly.

Yes, l_f is a list of file paths.

Before trying to help with debugging your issue: could you post the output of xr.show_versions()? That would help narrowing down on whether it's a dependency issue or a bug in xarray.

Here is the output: ``` In [2]: xr.show_versions()

INSTALLED VERSIONS

commit: None python: 3.6.9 |Anaconda, Inc.| (default, Jul 30 2019, 19:07:31) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 3.10.0-514.2.2.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: fr_CA.UTF-8 LOCALE: fr_CA.UTF-8 libhdf5: 1.10.4 libnetcdf: 4.6.1

xarray: 0.15.2.dev29+g6048356 pandas: 1.0.1 numpy: 1.18.1 scipy: 1.4.1 netCDF4: 1.4.2 pydap: None h5netcdf: None h5py: 2.9.0 Nio: None zarr: None cftime: 1.0.4.2 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: 1.3.1 dask: 2.10.1 distributed: 2.10.0 matplotlib: 3.0.2 cartopy: 0.16.0 seaborn: 0.9.0 numbagg: None pint: 0.9 setuptools: 45.2.0.post20200210 pip: 20.0.2 conda: None pytest: 5.3.4 IPython: 7.8.0 sphinx: 2.4.0

```

Also, could you try to demonstrate your issue using a synthetic example? I've been trying to reproduce it with:

python In [14]: units = 'days since 2000-02-25' ...: times = cftime.num2date(np.arange(7), units=units, calendar='365_day') ...: for x in range(5): ...: ds = xr.DataArray( ...: np.arange(x, 7 + x).reshape(7, 1), ...: coords={"time": times, "x": [x]}, ...: dims=['time', "x"], ...: name='a', ...: ).to_dataset() ...: ds.to_netcdf(f'data-noleap{x}.nc') ...: paths = sorted(glob.glob("data-noleap*.nc")) ...: with xr.open_mfdataset(paths, combine="by_coords") as ds: ...: print(ds.time.encoding) ...: {'zlib': False, 'shuffle': False, 'complevel': 0, 'fletcher32': False, 'contiguous': True, 'chunksizes': None, 'source': '.../data-noleap0.nc', 'original_shape': (7,), 'dtype': dtype('int64'), 'units': 'days since 2000-02-25 00:00:00.000000', 'calendar': 'noleap'} I used your code and it works for me also. I noticed the synthetic file is NETCDF4 and has int time variable while my files are NETCDF4_CLASSIC and the time variable is double. I modified the synthetic code to produce NETCDF4_CLASSIC files with double time variable but it does not change the results: encoding does not have any values related to the calendar.

Here is an output ouf ncdump -hs for one file, maybe it could help.

``` 11:41 neree ~/travail/xarray_open_mfdataset_perd_time_attributes :ncdump -hs /expl6/climato/arch/bbw/series/200001/snw_bbw_200001_se.nc netcdf snw_bbw_200001_se { dimensions: height = 1 ; rlat = 300 ; rlon = 340 ; time = UNLIMITED ; // (248 currently) variables: double height(height) ; height:units = "m" ; height:long_name = "height" ; height:standard_name = "height" ; height:axis = "Z" ; height:positive = "up" ; height:coordinate_defines = "point" ; height:actual_range = 0., 0. ; height:_Storage = "chunked" ; height:_ChunkSizes = 1 ; height:_DeflateLevel = 6 ; height:_Endianness = "little" ; double lat(rlat, rlon) ; lat:units = "degrees_north" ; lat:long_name = "latitude" ; lat:standard_name = "latitude" ; lat:actual_range = 7.83627367019653, 82.5695037841797 ; lat:_Storage = "chunked" ; lat:_ChunkSizes = 50, 50 ; lat:_DeflateLevel = 6 ; lat:_Endianness = "little" ; double lon(rlat, rlon) ; lon:units = "degrees_east" ; lon:long_name = "longitude" ; lon:standard_name = "longitude" ; lon:actual_range = -179.972747802734, 179.975296020508 ; lon:_Storage = "chunked" ; lon:_ChunkSizes = 50, 50 ; lon:_DeflateLevel = 6 ; lon:_Endianness = "little" ; double rlat(rlat) ; rlat:long_name = "latitude in rotated pole grid" ; rlat:units = "degrees" ; rlat:standard_name = "grid_latitude" ; rlat:axis = "Y" ; rlat:coordinate_defines = "point" ; rlat:actual_range = -30.7100009918213, 35.0699996948242 ; rlat:_Storage = "chunked" ; rlat:_ChunkSizes = 50 ; rlat:_DeflateLevel = 6 ; rlat:_Endianness = "little" ; double rlon(rlon) ; rlon:long_name = "longitude in rotated pole grid" ; rlon:units = "degrees" ; rlon:standard_name = "grid_longitude" ; rlon:axis = "X" ; rlon:coordinate_defines = "point" ; rlon:actual_range = -33.9900054931641, 40.5899810791016 ; rlon:_Storage = "chunked" ; rlon:_ChunkSizes = 50 ; rlon:_DeflateLevel = 6 ; rlon:_Endianness = "little" ; char rotated_pole ; rotated_pole:grid_mapping_name = "rotated_latitude_longitude" ; rotated_pole:grid_north_pole_latitude = 42.5f ; rotated_pole:grid_north_pole_longitude = 83.f ; rotated_pole:north_pole_grid_longitude = 0.f ; float snw(time, rlat, rlon) ; snw:units = "kg m-2" ; snw:long_name = "Surface Snow Amount" ; snw:standard_name = "surface_snow_amount" ; snw:realm = "landIce land" ; snw:cell_measures = "area: areacella" ; snw:coordinates = "lon lat" ; snw:grid_mapping = "rotated_pole" ; snw:level_desc = "Height" ; snw:cell_methods = "time: point" ; snw:_Storage = "chunked" ; snw:_ChunkSizes = 250, 50, 50 ; snw:_DeflateLevel = 6 ; snw:_Endianness = "little" ; double time(time) ; time:long_name = "time" ; time:standard_name = "time" ; time:axis = "T" ; time:calendar = "gregorian" ; time:units = "days since 2000-01-01 00:00:00" ; time:coordinate_defines = "point" ; time:_Storage = "chunked" ; time:_ChunkSizes = 250 ; time:_DeflateLevel = 6 ; time:_Endianness = "little" ;

// global attributes: :Conventions = "CF-1.6" ; :contact = "paquin.dominique@ouranos.ca" ; :comment = "CRCM5 v3331 0.22 deg AMNO22d2 L56 S17-15m ERA-INTERIM 0,75d PILSPEC PS3" ; :creation_date = "2016-08-15 " ; :experiment = "simulation de reference " ; :experiment_id = "bbw" ; :driving_experiment = "ERA-INTERIM " ; :driving_model_id = "ECMWF-ERAINT " ; :driving_model_ensemble_member = "r1i1p1 " ; :driving_experiment_name = "evaluation " ; :institution = "Ouranos " ; :institute_id = "Our. " ; :model_id = "OURANOS-CRCM5" ; :rcm_version_id = "v3331" ; :project_id = "" ; :ouranos_domain_name = "AMNO22d2 " ; :ouranos_run_id = "bbw OURALIB 1.3" ; :product = "output" ; :reference = "http://www.ouranos.ca" ; :history = "Mon Nov 7 10:13:55 2016: ncks -O --chunk_policy g3d --cnk_dmn plev,1 --cnk_dmn rlon,50 --cnk_dmn rlat,50 --cnk_dmn time,250 /localscratch/72194520.gm-1r16-n04.guillimin.clumeq.ca/bbw/bbw/200001/nc4c_snw_bbw_200001_se.nc /localscratch/72194520.gm-1r16-n04.guillimin.clumeq.ca/bbw/bbw/200001/snw_bbw_200001_se.nc\n", "Mon Nov 7 10:13:50 2016: ncks -O --fl_fmt=netcdf4_classic -L 6 /localscratch/72194520.gm-1r16-n04.guillimin.clumeq.ca/bbw/bbw/200001/trim_snw_bbw_200001_se.nc /localscratch/72194520.gm-1r16-n04.guillimin.clumeq.ca/bbw/bbw/200001/nc4c_snw_bbw_200001_se.nc\n", "Mon Nov 7 10:13:48 2016: ncks -d time,2000-01-01 00:00:00,2000-01-31 23:59:59 /home/dpaquin1/postprod/bbw/transit2/200001/snw_bbw_200001_se.nc /localscratch/72194520.gm-1r16-n04.guillimin.clumeq.ca/bbw/bbw/200001/trim_snw_bbw_200001_se.nc\n", "Fri Nov 4 12:49:33 2016: ncks -4 -L 1 --no_tmp_fl -u -d time,2000-01-01 00:00,2000-02-01 00:00 /localscratch/72001487.gm-1r16-n04.guillimin.clumeq.ca/I5/snw_bbw_2000_se.nc /home/dpaquin1/postprod/bbw/work/200001/snw_bbw_200001_se.nc\n", "Fri Nov 4 12:48:52 2016: ncks -4 -L 1 /localscratch/72001487.gm-1r16-n04.guillimin.clumeq.ca/I5/snw_bbw_2000_se.nc /home/dpaquin1/postprod/bbw/work/2000/snw_bbw_2000_se.nc\n", "Fri Nov 4 12:48:44 2016: ncatted -O -a cell_measures,snw,o,c,area: areacella /localscratch/72001487.gm-1r16-n04.guillimin.clumeq.ca/I5/snw_bbw_2000_se.nc 25554_bbb" ; :NCO = "4.4.4" ; :_SuperblockVersion = 2 ; :_IsNetcdf4 = 1 ; :_Format = "netCDF-4 classic model" ; } ``` I guess the next option could be to go into xarray code to try to find what the problem is but I would need some direction for doing this.