[DOCS] Document date math support for aliases (#70535)

Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>

docs/reference/api-conventions.asciidoc

@@ -79,19 +79,17 @@ IMPORTANT: Direct access to system indices is deprecated and
 will no longer be allowed in the next major version.
 
 [[date-math-index-names]]
-=== Date math support in index names
+=== Date math support in index and index alias names
 
-Date math index name resolution enables you to search a range of time series indices, rather
-than searching all of your time series indices and filtering the results or maintaining aliases.
-Limiting the number of indices that are searched reduces the load on the cluster and improves
-execution performance. For example, if you are searching for errors in your
-daily logs, you can use a date math name template to restrict the search to the past
-two days.
+Date math name resolution lets you to search a range of time series indices or
+index aliases rather than searching all of your indices and filtering the
+results. Limiting the number of searched indices reduces cluster load and
+improves search performance. For example, if you are searching for errors in
+your daily logs, you can use a date math name template to restrict the search to
+the past two days.
 
-Almost all APIs that have an `index` parameter support date math in the `index` parameter
-value.
-
-A date math index name takes the following form:
+Most APIs that accept an index or index alias argument support date math. A date
+math name takes the following form:
 
 [source,txt]
 ----------------------------------------------------------------------
@@ -101,10 +99,10 @@ A date math index name takes the following form:
 Where:
 
 [horizontal]
-`static_name`:: is the static text part of the name
-`date_math_expr`:: is a dynamic date math expression that computes the date dynamically
-`date_format`:: is the optional format in which the computed date should be rendered. Defaults to `yyyy.MM.dd`. Format should be compatible with java-time https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
-`time_zone`:: is the optional time zone. Defaults to `utc`.
+`static_name`:: Static text
+`date_math_expr`:: Dynamic date math expression that computes the date dynamically
+`date_format`:: Optional format in which the computed date should be rendered. Defaults to `yyyy.MM.dd`. Format should be compatible with java-time https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
+`time_zone`:: Optional time zone. Defaults to `UTC`.
 
 NOTE: Pay attention to the usage of small vs capital letters used in the `date_format`. For example:
 `mm` denotes minute of hour, while `MM` denotes month of year. Similarly `hh` denotes the hour in the
@@ -113,8 +111,8 @@ NOTE: Pay attention to the usage of small vs capital letters used in the `date_f
 Date math expressions are resolved locale-independent. Consequently, it is not possible to use any other
 calendars than the Gregorian calendar.
 
-You must enclose date math index name expressions within angle brackets, and
-all special characters should be URI encoded. For example:
+You must enclose date math names in angle brackets. If you use the name in a
+request path, special characters must be URI encoded. For example:
 
 [source,console]
 ----
@@ -139,8 +137,8 @@ The special characters used for date rounding must be URI encoded as follows:
 `,`:: `%2C`
 ======================================================
 
-The following example shows different forms of date math index names and the final index names
-they resolve to given the current time is 22nd March 2024 noon utc.
+The following example shows different forms of date math names and the final names
+they resolve to given the current time is 22nd March 2024 noon UTC.
 
 [options="header"]
 |======
@@ -152,7 +150,7 @@ they resolve to given the current time is 22nd March 2024 noon utc.
 | `<logstash-{now/d{yyyy.MM.dd\|+12:00}}>`  | `logstash-2024.03.23`
 |======
 
-To use the characters `{` and `}` in the static part of an index name template, escape them
+To use the characters `{` and `}` in the static part of a name template, escape them
 with a backslash `\`, for example:
 
  * `<elastic\\{ON\\}-{now/M}>` resolves to `elastic{ON}-2024.03.01`

docs/reference/indices/add-alias.asciidoc

@@ -47,7 +47,8 @@ NOTE: You cannot add <<data-streams,data streams>> to an index alias.
 
 `<alias>`::
 (Required, string)
-Name of the index alias to create or update.
+Name of the index alias to create or update. Supports
+<<date-math-index-names,date math>>.
 
 
 [[add-alias-api-query-params]]
@@ -68,6 +69,18 @@ include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=index-routing]
 [[add-alias-api-example]]
 ==== {api-examples-title}
 
+[[alias-date-math-support]]
+===== Date math support
+
+Index alias names support <<date-math-index-names,date math>>.
+
+[source,console]
+----
+# POST /logs/_alias/<logs_{now/M}>
+POST /logs/_alias/%3Clogs_%7Bnow%2FM%7D%3E
+----
+// TEST[s/^/PUT logs\n/]
+
 [[alias-adding]]
 ===== Add a time-based alias
 
@@ -139,3 +152,16 @@ PUT /logs_20302801
   }
 }
 --------------------------------------------------
+
+The create index API also supports <<date-math-index-names,date math>> in index
+alias names.
+
+[source,console]
+----
+PUT /logs
+{
+  "aliases": {
+    "<logs_{now/M}>": {}
+  }
+}
+----

docs/reference/indices/aliases.asciidoc

@@ -103,19 +103,19 @@ NOTE: You cannot add <<data-streams,data streams>> to an index alias.
 
 `alias`::
 (String)
-Comma-separated list or wildcard expression of index alias names to
-add, remove, or delete.
+Comma-separated list or wildcard expression of index alias names to add, remove,
+or delete. Supports <<date-math-index-names,date math>>.
 +
 If the `aliases` parameter is not specified,
 this parameter is required for the `add` or `remove` action.
 
 `aliases`::
 (Array of strings)
-Array of index alias names to
-add, remove, or delete.
+Array of index alias names to add, remove, or delete. Supports
+<<date-math-index-names,date math>>.
 +
-If the `alias` parameter is not specified,
-this parameter is required for the `add` or `remove` action.
+If the `alias` parameter is not specified, this parameter is required for the
+`add` or `remove` action.
 
 `filter`::
 (Optional, query object)
@@ -190,6 +190,20 @@ POST /_aliases
 --------------------------------------------------
 // TEST[s/^/PUT test1\nPUT test2\n/]
 
+Index alias names support <<date-math-index-names,date math>>.
+
+[source,console]
+----
+POST /_aliases
+{
+  "actions" : [
+    { "add" : { "index" : "logs", "alias" : "<logs_{now/M}>" } }
+  ]
+}
+----
+// TEST[s/^/PUT logs\n/]
+// TEST[continued]
+
 [[indices-aliases-api-remove-alias-ex]]
 ===== Remove an alias
 

docs/reference/indices/create-index.asciidoc

@@ -68,7 +68,7 @@ include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=timeoutparms]
 
 `aliases`::
 (Optional, <<indices-aliases,alias object>>) Index aliases which include the
-index. See <<indices-aliases>>.
+index. Index alias names support <<date-math-index-names,date math>>.
 
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=mappings]
 
@@ -161,6 +161,18 @@ PUT /test
 }
 --------------------------------------------------
 
+Index alias names also support <<date-math-index-names,date math>>.
+
+[source,console]
+----
+PUT /logs
+{
+  "aliases": {
+    "<logs_{now/M}>": {}
+  }
+}
+----
+
 [[create-index-wait-for-active-shards]]
 ===== Wait for active shards
 
@@ -173,7 +185,7 @@ what happened:
 {
   "acknowledged": true,
   "shards_acknowledged": true,
-  "index": "test"
+  "index": "logs"
 }
 --------------------------------------------------
 

docs/reference/rest-api/common-parms.asciidoc

@@ -25,15 +25,16 @@ end::index-alias[]
 
 tag::aliases[]
 `aliases`::
-(Optional, <<indices-aliases,alias object>>) Index aliases which include the
-index. See <<indices-aliases>>.
+(Optional, <<indices-aliases,alias object>>) <<indices-aliases,Index aliases>>
+which include the index. Index alias names support <<date-math-index-names,date
+math>>.
 end::aliases[]
 
 tag::target-index-aliases[]
 `aliases`::
 (Optional, <<indices-aliases,alias object>>)
-Index aliases which include the target index.
-See <<indices-aliases>>.
+<<indices-aliases,Index aliases>> which include the target index. Index alias
+names support <<date-math-index-names,date math>>.
 end::target-index-aliases[]
 
 tag::allow-no-indices[]