issue_comments: 1530347592

Ah hah! Well, I don't know why this is working for you @kmuehlbauer, but I can see why it is not working for me. I've been debugging through the code and it looks like the problem is the _decode_datetime_with_pandas function. For me, it's converting a float NaN into an integer, which results in a zero value.

It all starts in the open_zarr function, which by default sets the use_cftime parameter to None by default: https://github.com/pydata/xarray/blob/25d9a28e12141b9b5e4a79454eb76ddd2ee2bc4d/xarray/backends/zarr.py#L701-L817

There's a bunch of stuff that gets called, but eventually we get to the function decode_cf_datetime, which ironically (given the name) also takes this use_cftime parameter, which is still None. Because use_cftime is None, the function calls _decode_datetime_with_pandas:

https://github.com/pydata/xarray/blob/25d9a28e12141b9b5e4a79454eb76ddd2ee2bc4d/xarray/coding/times.py#L265-L289

and then, in _decode_datetime_with_pandas, the code casts a float NaN value to zero:

https://github.com/pydata/xarray/blob/979b99831f5d34d33120312a15dad3e6a0830f32/xarray/coding/times.py#L216-L262

In line 254, flat_num_dates is array([ nan, 1.6726176e+18]). After line 254, flat_nuM-dates_ns_int is array([ 0, 1672617600000000000]).