issues: 484699415

This data as json

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
484699415 MDU6SXNzdWU0ODQ2OTk0MTU= 3256 .item() on a DataArray with dtype='datetime64[ns]' returns int 1778852 open 0     4 2019-08-23T20:29:50Z 2022-04-09T02:03:43Z   NONE      

MCVE Code Sample

```python import datetime import xarray as xr

test_da = xr.DataArray(datetime.datetime(2019, 1, 1, 1, 1))

test_da

<xarray.DataArray ()>

array('2019-01-01T01:01:00.000000000', dtype='datetime64[ns]')

test_da.item()

1546304460000000000

```

Expected Output

I would think it would be nice to get a datetime out of the .item() call then the nanosecond representation.

Output of xr.show_versions()

When I call xr.show_versions() i get an error but im running xarray 0.12.3 
{
    "url": "https://api.github.com/repos/pydata/xarray/issues/3256/reactions",
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
     13221727 issue

Links from other tables