html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/pull/134#issuecomment-43545468,https://api.github.com/repos/pydata/xarray/issues/134,43545468,MDEyOklzc3VlQ29tbWVudDQzNTQ1NDY4,514053,2014-05-19T19:27:26Z,2014-05-19T19:27:26Z,CONTRIBUTOR,"Also worth considering: how should datetime64[us] datetimes be handled?  Currently they get cast to [ns] which, since datetimes do not, could get confusing.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,33772168
https://github.com/pydata/xarray/pull/134#issuecomment-43535578,https://api.github.com/repos/pydata/xarray/issues/134,43535578,MDEyOklzc3VlQ29tbWVudDQzNTM1NTc4,514053,2014-05-19T17:55:00Z,2014-05-19T17:55:00Z,CONTRIBUTOR,"Yeah all fixed.

In #125 I went the route of forcing datetimes to be datetime64[ns].  This is probably part of a broader conversation, but doing so might save some future headaches.  Of course ... it would also restrict us to nanosecond precision.  Basically I feel like we should either force datetimes to be datetime64[ns] or make sure that operations on datetime objects preserve their type.

Probably worth getting this in and picking that conversation back up if needed.  In which case could you add tests which make sure variables with datetime objects are still datetime objects after concatenation?  If those start getting cast to datetime[ns] it'll start get confusing for users.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,33772168
https://github.com/pydata/xarray/pull/134#issuecomment-43473367,https://api.github.com/repos/pydata/xarray/issues/134,43473367,MDEyOklzc3VlQ29tbWVudDQzNDczMzY3,514053,2014-05-19T07:35:53Z,2014-05-19T07:35:53Z,CONTRIBUTOR,"The reorganization does make things cleaner, but the behavior changed relative to #125.  In particular, while this patch fixes concatenation with datetime64 times it doesn't work with datetimes:

```
In [2]: dates = [datetime.datetime(2011, 1, i + 1) for i in range(10)]
In [3]: ds = xray.Dataset({'time': ('time', dates)})
In [4]: xray.Dataset.concat([ds.indexed(time=slice(0, 4)), ds.indexed(time=slice(4, 8))], 'time')['time'].values
Out[4]: 
array([1293840000000000000L, 1293926400000000000L, 1294012800000000000L,
       1294099200000000000L, 1294185600000000000L, 1294272000000000000L,
       1294358400000000000L, 1294444800000000000L], dtype=object)
```

and not sure if this was broken before or not ...

```
In [5]: xray.Dataset.concat([x for _, x in ds.groupby('time')], 'time')['time'].values
ValueError: cannot slice a 0-d array
```
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,33772168