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/issues/2921#issuecomment-490143871,https://api.github.com/repos/pydata/xarray/issues/2921,490143871,MDEyOklzc3VlQ29tbWVudDQ5MDE0Mzg3MQ==,2448579,2019-05-07T16:04:58Z,2019-05-07T16:06:39Z,MEMBER,"Thanks for the great report @klindsay28. 

Looks like [CF recommends ](http://cfconventions.org/cf-conventions/cf-conventions.html#cell-boundaries) that `time_bounds` (boundary variable) not have the `units` or `calendar` attributes:
> Since a boundary variable is considered to be part of a coordinate variable’s metadata, it is not necessary to provide it with attributes such as long_name and units.

> Boundary variable attributes which determine the coordinate type (units, standard_name, axis and positive) or those which affect the interpretation of the array values (units, calendar, leap_month, leap_year and month_lengths) must always agree exactly with the same attributes of its associated coordinate, scalar coordinate or auxiliary coordinate variable. To avoid duplication, however, it is recommended that these are not provided to a boundary variable.

We already have special treatment for `time_bounds` in the decode step. It makes sense to treat it specially in the encode step. In fact it looks like @spencerkclark identified this issue in https://github.com/pydata/xarray/pull/2571 :clap:

@klindsay28 Any interest in putting together a PR that would avoid setting these attributes on `time_bounds` during the encode step?

Ping @fmaussion for feedback.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,437418525