Support partial ISO8601 dates in queries

[rmccue]

Right now, we support sending date or modified with a full ISO 8601 date (yyyy-mm-ddThh:ii:ssZ), and we also support before and after. However, there's no easy way to get posts for a certain month, without building the before and after yourself.

​ISO 8601 gives us a way to specify partial dates: yyyy and yyyy-mm are both valid, and we could totally support them. This avoids the need for a separate year or month query parameter. Internally, this can map to before and after values.

[joehoyle]

Internally, this can map to before and after values.

If these go to before and after values, does that mean that ?date=2014 returns all posts after 2014? I presume someone would mean "only get posts from 2014" with that?

[rmccue]

Replying to joehoyle:

If these go to before and after values, does that mean that ?date=2014 returns all posts after 2014? I presume someone would mean "only get posts from 2014" with that?

Note: "and"

date=2014 would map to after=2013-12-31T23:59:59&before=2015-01-01T00:00:00

[kadamwhite]

I like this idea a lot; it's a much more elegant way to find a specific time period than passing two full ISO date strings with tailored T values just to get a month or a day of content

[rmccue]

Punting to 4.8.

[LaustDeleuran]

#38986 was marked as a duplicate.

[LaustDeleuran]

Reacting late to @jnylen0's request to repost my issue from #38986 here. Basically, the documentation implies full ISO 8601 compliance, but the API only works when you include a full date and time, ie. YYYY-MM-DDTHH:MM:SS. For instance, this fails, even though I'm passing a valid ISO 8601 date:
​http://demo.wp-api.org/wp-json/wp/v2/posts?before=2016-11-29

The documentation should either specify the specific format that the before/after parameters require, or support full ISO 8601. In my opinion, the latter would be preferred.

Thanks.