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/940#issuecomment-239210833,https://api.github.com/repos/pydata/xarray/issues/940,239210833,MDEyOklzc3VlQ29tbWVudDIzOTIxMDgzMw==,950575,2016-08-11T16:15:05Z,2016-08-11T16:15:05Z,CONTRIBUTOR,"@shoyer the more I think about this the more I don't like the addition of extra keywords. Even though I would like this behavior to be the default one I really do not like the complexity I added here.

Closing this...
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,169276671
https://github.com/pydata/xarray/pull/940#issuecomment-237659233,https://api.github.com/repos/pydata/xarray/issues/940,237659233,MDEyOklzc3VlQ29tbWVudDIzNzY1OTIzMw==,950575,2016-08-04T19:33:35Z,2016-08-04T19:33:35Z,CONTRIBUTOR,"> If the main issue is plotting, you could try fixing that upstream, too! pydata/pandas#8711

Indeed! That makes sense to matter what is decided here. Thanks for pointing that out. (Not sure if I am up to the challenge though.)

> It might be worth querying the mailing list for more opinions here.

Done!
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,169276671
https://github.com/pydata/xarray/pull/940#issuecomment-237649523,https://api.github.com/repos/pydata/xarray/issues/940,237649523,MDEyOklzc3VlQ29tbWVudDIzNzY0OTUyMw==,950575,2016-08-04T18:57:14Z,2016-08-04T18:57:14Z,CONTRIBUTOR,"> Decoding time units into `timedelta64` is useful if you want to be able to use them for arithmetic with datetimes.

I get that but my question is how often do users perform do such operations? Again I am biased b/c with my data I never want to do that as it does not make sense. And, when it does make sense, I believe that the price of post conversion is worth the advantages of converting by `default`.

> Still I'm somewhat reluctant to change the default here.

If you want `decode_timedeltas=True` as the `default` I am not sure it is worth the extra keyword then. My goal with this PR is to avoid extra steps. If users need to set it to `True` it is not too different from doing `data.values / 1e9`. If all we get is to change one step for another I prefer to not make the `open_dataset` more complex and leave it as is.

Feel free to close this. I don't have strong feelings about what `xarray` should do by default. I just want to make it more convenient for my uses cases.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,169276671
https://github.com/pydata/xarray/pull/940#issuecomment-237560363,https://api.github.com/repos/pydata/xarray/issues/940,237560363,MDEyOklzc3VlQ29tbWVudDIzNzU2MDM2Mw==,950575,2016-08-04T13:56:40Z,2016-08-04T13:56:40Z,CONTRIBUTOR,"This is ready for review.

[Here](http://nbviewer.jupyter.org/gist/ocefpaf/cabdcb27a5ef7da1b6110327a5f03e17) is an example of this PR in action showing how plotting and working with periods gets easier with `floats` instead of `timedeltas`.

BTW, in light of https://github.com/pydata/xarray/issues/939#issue-169274464, I wonder if `decode_timedeltas` and `decode_datetimes` (or even the original `decode_times`) are needed at all. (Just defending myself as I don't really want a new keyword argument but a better default for time data in general :grimacing:)

Maybe I am being thick and I don't know enough use cases data but I cannot see why someone might want to convert time data (which most of the time represent periods) to `timedeltas`. That breaks from the original data units and forces the user to compute it back and convert the `dtype` too before for plotting, etc.

Regarding time coordinate itself I understand that `xarray`, due to the pandas nature of the index, needs to fail to convert time when the calendar is not supported by pandas. Maybe, instead of throwing an error and asking the users to use the option `decode_(date)times=False` in case of failure, `xarray` could issue an warning and return only the ""numbers"" as if `decode_(date)times` were set to `False`.

I understand, and agree most of the time, that raising erros is better than issuing warnings, and creating an ambiguity in the returns. So maybe this one is harder to change than the former.
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