By default, the date histogram aggregation format should be left blank (or set to date_optional_time)

[nascosto]

In, DateHistogramAggregationDescriptor, the date format is being set to "yyyy-MM-dd" here. This creates confusion (at least is really did for me), because date strings that are input into extended_bounds require the same format. This means that intervals of seconds, minutes, etc. are off limits unless you change the format back to ISO format (months, years, etc. work fine with ISO format).

It would probably be best to just not serialize the format by default unless the value is actually set by the user.

[gmarz]

Hi @nascosto

Totally agree here. We should just accept the default format from elasticsearch instead of setting it to yyyy-MM-dd, unless of course the user explicitly sets it. Great catch and thank you for reporting.

My only reservation is that changing this now would be considered a breaking change. @Mpdreamz what are your thoughts? This might be a 2.0 thing.

[Mpdreamz]

Im in favor of leaving format empty by default and don't think its a bwc thing