This should get localized and we should remove the hours, minutes, secs. There is some config in the date config that indicates if we are displaying months or years.

When you say date config, are you referring to a query value that could be specified in the API request?

Ya there is interval information from the widget filter config: https://cloudup.com/cD3amQW3Ba1

That should be applied both for the API request and for determining how to display the results (if year, then only show the year, if month, then show year and month).

Could we push the interval formatting and localization to the API? Otherwise, we'll need to consider adding a date formatting library to the client, which could add a minimum of 15kB to our production bundle.

The interval value is already being passed in the API call.

Possibly ya. Is the 15kb from pulling in https://www.npmjs.com/package/@wordpress/date which looks like it includes date_i18n()? We may want something like this anyways to correctly display in search results though.

I think the count comes from the config.

The API currently throws a 400 when I specify a size query value for aggregations[date_histogram_0][date_histogram][size]. See this example query.

Ya, the api will always return all of them, but we have an option (https://cloudup.com/cD3amQW3Ba1) that lets the user indicate how many to show. 5 shouldn't be hard coded.

Is it possible to support the size query value as it does for taxonomy and post_type aggregations?

In the meanwhile, I'll look into linking up the widget configuration values to the aggregation values in the client in a follow-up PR.

ES doesn't support it itself, so we would have to post process is somehow on the API side. I'd rather not deviate from the ES standards for aggs and filters though as that could make things harder to support long term.