From f71f2a097a00c7bc3fa48190e2ca4e5ac333c1eb Mon Sep 17 00:00:00 2001 From: Sue-Gallagher Date: Fri, 13 Jul 2018 09:56:09 -0700 Subject: [PATCH] [DOCS] Add info on calendar v fixed interval. Closes #29410 --- .../bucket/datehistogram-aggregation.asciidoc | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/docs/reference/aggregations/bucket/datehistogram-aggregation.asciidoc b/docs/reference/aggregations/bucket/datehistogram-aggregation.asciidoc index 8cfbf5ad94dff..824b05dcd61ca 100644 --- a/docs/reference/aggregations/bucket/datehistogram-aggregation.asciidoc +++ b/docs/reference/aggregations/bucket/datehistogram-aggregation.asciidoc @@ -343,6 +343,16 @@ second document falls into the bucket for 1 October 2015: <1> The `key_as_string` value represents midnight on each day in the specified timezone. +WARNING: When using time zones that follow DST (daylight savings time) changes, +buckets close to the moment when those changes happen can have slightly different +sizes than you would expect from the used `interval`. +For example, consider a DST start in the `CET` time zone: on 27 March 2016 at 2am, +clocks were turned forward 1 hour to 3am local time. If you use `day` as `interval`, +the bucket covering that day will only hold data for 23 hours instead of the usual +24 hours for other buckets. The same is true for shorter intervals, like 12h, +where you'll have only a 11h bucket on the morning of 27 March when the DST shift +happens. + ===== Offset Use the `offset` parameter to change the start value of each bucket by the