Automatic snapshot naming elastic#7939

extended doc: example is added. referring to indices date math more clearly

Author: Vladimir Dolzhenko

docs/reference/modules/snapshots.asciidoc

@@ -282,14 +282,26 @@ PUT /_snapshot/my_backup/snapshot_2?wait_for_completion=true
 // TEST[continued]
 
 The list of indices that should be included into the snapshot can be specified using the `indices` parameter that
-supports <<multi-index,multi index syntax>>. It can be useful to use <<date-math-index-names,date math>> to name the
-snapshot according to the date that the snapshot made, e.g. `snapshot-2018.05.09`.  The snapshot request also supports the
+supports <<multi-index,multi index syntax>>. The snapshot request also supports the
 `ignore_unavailable` option. Setting it to `true` will cause indices that do not exist to be ignored during snapshot
 creation. By default, when `ignore_unavailable` option is not set and an index is missing the snapshot request will fail.
 By setting `include_global_state` to false it's possible to prevent the cluster global state to be stored as part of
 the snapshot. By default, the entire snapshot will fail if one or more indices participating in the snapshot don't have
 all primary shards available. This behaviour can be changed by setting `partial` to `true`.
 
+Snapshot could be named according to the date that the snapshot made in a similar way as indices
+using <<date-math-index-names,date math expressions>>, keep in mind all special characters should be URI encoded.
+
+For example, following command creates a snapshot with a name like `snapshot-2018.05.11`:
+[source,js]
+-----------------------------------
+# PUT /_snapshot/my_backup/<snapshot-{now/d}>
+PUT /_snapshot/my_backup/%3Csnapshot-%7Bnow%2Fd%7D%3E
+-----------------------------------
+// CONSOLE
+// TEST[continued]
+
+
 The index snapshot process is incremental. In the process of making the index snapshot Elasticsearch analyses
 the list of the index files that are already stored in the repository and copies only files that were created or
 changed since the last snapshot. That allows multiple snapshots to be preserved in the repository in a compact form.