Add some information on locale database to the ES docs

docs/reference/ingest/processors/date.asciidoc

@@ -67,3 +67,11 @@ the timezone and locale values.
 }
 --------------------------------------------------
 // NOTCONSOLE
+
+[WARNING]
+====
+// tag::locale-warning[]
+The text strings accepted by textual date formats, and calculations for week-dates, depend on the JDK version
+that Elasticsearch is running on. For more information see <<jdk-locale,locale database>>.
+// end::locale-warning[]
+====

docs/reference/mapping/types/date.asciidoc

@@ -81,6 +81,14 @@ on those dates so they should be avoided.
 // end::decimal-warning[]
 ====
 
+[WARNING]
+====
+// tag::locale-warning[]
+The text strings accepted by textual date formats, and calculations for week-dates, depend on the JDK version
+that Elasticsearch is running on. For more information see <<jdk-locale,locale database>>.
+// end::locale-warning[]
+====
+
 [[multiple-date-formats]]
 ==== Multiple date formats
 
@@ -126,7 +134,7 @@ The following parameters are accepted by `date` fields:
 
     The locale to use when parsing dates since months do not have the same names
     and/or abbreviations in all languages. The default is the
-    https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#ROOT[`ROOT` locale],
+    https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#ROOT[`ROOT` locale].
 
 <<ignore-malformed,`ignore_malformed`>>::
 

docs/reference/setup/install.asciidoc

@@ -5,8 +5,8 @@
 [[hosted-elasticsearch-service]]
 === Hosted Elasticsearch Service
 
-{ecloud} offers all of the features of {es}, {kib}, and  Elastic’s {observability}, {ents}, and {elastic-sec} solutions as a hosted service 
-available on AWS, GCP, and Azure. 
+{ecloud} offers all of the features of {es}, {kib}, and  Elastic’s {observability}, {ents}, and {elastic-sec} solutions as a hosted service
+available on AWS, GCP, and Azure.
 
 To set up Elasticsearch in {ecloud}, sign up for a {ess-trial}[free {ecloud} trial].
 
@@ -17,7 +17,7 @@ To set up Elasticsearch in {ecloud}, sign up for a {ess-trial}[free {ecloud} tri
 If you want to install and manage {es} yourself, you can:
 
 * Run {es} using a <<elasticsearch-install-packages,Linux, MacOS, or Windows install package>>.
-* Run {es} in a <<elasticsearch-docker-images,Docker container>>. 
+* Run {es} in a <<elasticsearch-docker-images,Docker container>>.
 * Set up and manage {es}, {kib}, {agent}, and the rest of the Elastic Stack on Kubernetes with {eck-ref}[{eck}].
 
 TIP: To try out Elasticsearch on your own machine, we recommend using Docker and running both Elasticsearch and Kibana. For more information, see <<run-elasticsearch-locally,Run Elasticsearch locally>>. Please note that this setup is *not suitable for production use*.
@@ -98,6 +98,18 @@ the bundled JVM are treated as if they were within {es} itself.
 The bundled JVM is located within the `jdk` subdirectory of the {es} home
 directory. You may remove this directory if using your own JVM.
 
+[discrete]
+[[jdk-locale]]
+=== JDK locale database
+
+The locale database used by {es}, used to map from various date formats to
+the underlying date storage format, depends on the version of the JDK
+that {es} is running on. On JDK version 23 and above, {es} will use the
+_CLDR_ database. On JDK version 22 and below, {es} will use the _COMPAT_
+database. This may mean that the strings used for textual date formats,
+and the output of custom week-date formats, may change when moving from
+a previous JDK version to JDK 23 or above.
+
 [discrete]
 [[jvm-agents]]
 === JVM and Java agents