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
232623945,MDU6SXNzdWUyMzI2MjM5NDU=,1435,xarray.plot.imshow with datetime coordinates results in blank plot,500246,open,0,,,6,2017-05-31T16:31:30Z,2022-05-03T01:56:37Z,,CONTRIBUTOR,,,,"```
In [72]: da = xarray.DataArray(arange(5*6).reshape(5,6), dims=(""A"", ""B""), coords={""A"": arange(5), ""B"": pd.date_range(""2000-01-01"", periods=6)})

In [73]: da.plot.imshow()
Out[73]: <matplotlib.image.AxesImage at 0x7f699cf1acf8>
```

The resulting plot has the correct axes and colorbar, but the contents of the plot itself are blank.  Upon moving the cursor over the plot, there is an exception in `Tkinter`:

```
Exception in Tkinter callback
Traceback (most recent call last):
  File ""/home/users/gholl/lib/python3.5/tkinter/__init__.py"", line 1549, in __call__
    return self.func(*args)
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/backends/backend_tkagg.py"", line 387, in motion_notify_event
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=event)
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/backend_bases.py"", line 1966, in motion_notify_event
    self.callbacks.process(s, event)
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/cbook.py"", line 554, in process
    proxy(*args, **kwargs)
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/cbook.py"", line 416, in __call__
    return mtd(*args, **kwargs)
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/backend_bases.py"", line 2857, in mouse_move
    artists = [a for a in event.inaxes.mouseover_set
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/backend_bases.py"", line 2858, in <listcomp>
    if a.contains(event) and a.get_visible()]
  File ""/dev/shm/gerrit/venv/stable-3.5/lib/python3.5/site-packages/matplotlib/image.py"", line 567, in contains
    inside = ((x >= xmin) and (x <= xmax) and
TypeError: invalid type promotion
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/1435/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue