issues: 154924822

Hi, all

Recently, I found a error about time decoding. The .nc file is POP output.

``` Python In [29]: ds = xr.open_mfdataset('EXAMPLE_CASE.pop.h.0001-01.nc')

---

ValueError Traceback (most recent call last) <ipython-input-29-576c2580c841> in <module>() ----> 1 ds = xr.open_mfdataset('EXAMPLE_CASE.pop.h.0001-01.nc')

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/backends/api.pyc in open_mfdataset(paths, chunks, concat_dim, preprocess, engine, lock, kwargs) 300 lock = _default_lock(paths[0], engine) 301 datasets = [open_dataset(p, engine=engine, chunks=chunks or {}, lock=lock, --> 302 kwargs) for p in paths] 303 file_objs = [ds._file_obj for ds in datasets] 304

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/backends/api.pyc in open_dataset(filename_or_obj, group, decode_cf, mask_and_scale, decode_times, concat_characters, decode_coords, engine, chunks, lock, drop_variables) 225 lock = _default_lock(filename_or_obj, engine) 226 with close_on_error(store): --> 227 return maybe_decode_store(store, lock) 228 else: 229 if engine is not None and engine != 'scipy':

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/backends/api.pyc in maybe_decode_store(store, lock) 156 store, mask_and_scale=mask_and_scale, decode_times=decode_times, 157 concat_characters=concat_characters, decode_coords=decode_coords, --> 158 drop_variables=drop_variables) 159 160 if chunks is not None:

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/conventions.pyc in decode_cf(obj, concat_characters, mask_and_scale, decode_times, decode_coords, drop_variables) 888 vars, attrs, coord_names = decode_cf_variables( 889 vars, attrs, concat_characters, mask_and_scale, decode_times, --> 890 decode_coords, drop_variables=drop_variables) 891 ds = Dataset(vars, attrs=attrs) 892 ds = ds.set_coords(coord_names.union(extra_coords))

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/conventions.pyc in decode_cf_variables(variables, attributes, concat_characters, mask_and_scale, decode_times, decode_coords, drop_variables) 823 new_vars[k] = decode_cf_variable( 824 v, concat_characters=concat, mask_and_scale=mask_and_scale, --> 825 decode_times=decode_times) 826 if decode_coords: 827 var_attrs = new_vars[k].attrs

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/conventions.pyc in decode_cf_variable(var, concat_characters, mask_and_scale, decode_times, decode_endianness) 764 units = pop_to(attributes, encoding, 'units') 765 calendar = pop_to(attributes, encoding, 'calendar') --> 766 data = DecodedCFDatetimeArray(data, units, calendar) 767 elif attributes['units'] in TIME_UNITS: 768 # timedelta

/Users/Yefee/miniconda2/lib/python2.7/site-packages/xarray/conventions.pyc in init(self, array, units, calendar) 389 if not PY3: 390 msg += ' Full traceback:\n' + traceback.format_exc() --> 391 raise ValueError(msg) 392 else: 393 self._dtype = getattr(result, 'dtype', np.dtype('object'))

ValueError: unable to decode time units u'days since 0000-01-01 00:00:00' with the default calendar. Try opening your dataset with decode_times=False.` ```

The actual time is:

``` 31 double time(time) ;

32 time:long_name = "time" ;

33 time:units = "days since 0000-01-01 00:00:00" ;

34 time:bounds = "time_bound" ;

35 time:calendar = "noleap" ; ```

I can set 'decode_times=False' to open the file but the time is not right.

``` Coordinates: transport_components (transport_comp) |S256 'Total' ... transport_regions (transport_reg) |S256 'Global Ocean - Marginal Seas' ... * time (time) float64 396.0

Is there any suggestions? ``````