issue_comments: 441226736

@fmaussion I have run into this issue before and it is a bit cumbersome. My workaround in the past has been to open the dataset without decoding the times initially, copy the units and calendar attributes from the time variable to the time_bnds variable, and then decode the times (xarray will decode any variable with a time-like units attribute into dates, regardless of its name).

``` In [1]: import xarray

In [2]: ds = xarray.open_dataset('cesm.TREFHT.160001-200512.selection.nc', decode_times=False)

In [3]: ds.time_bnds.attrs['units'] = ds.time.attrs['units']

In [4]: ds.time_bnds.attrs['calendar'] = ds.time.attrs['calendar']

In [5]: ds_decoded = xarray.decode_cf(ds) ```

I am actually in favor of 3: also decode time_bnds

It would be nice if we could handle this automatically, though one issue that concerns me is how we would automatically determine which variable represents the time bounds in an arbitrary netCDF file (as mentioned above we currently do not have any variable-name-specific logic in xarray, which I think is a good thing). I do notice the time variable in your file has a bounds attribute, which points to the name time_bnds. Is that something required by CF conventions? We might be able to rely on that.