Add one example with offset

Author: bpintea

docs/reference/esql/functions/examples/bucket.asciidoc

@@ -145,6 +145,24 @@ AVG(salary):double | bucket:date
 // end::bucket_in_agg-result[]
 ;
 
+bucketWithOffset#[skip:-8.13.99, reason:BUCKET renamed in 8.14]
+// tag::bucketWithOffset[]
+FROM employees 
+| STATS dates = values(birth_date) BY b = BUCKET(birth_date + 1 hour, 1 year) - 1 hour
+| EVAL d_count = MV_COUNT(dates)
+| SORT d_count
+| LIMIT 3
+// end::bucketWithOffset[]
+;
+
+// tag::bucketWithOffset-result[]
+dates:date                                                                                              |b:date                  |d_count:integer
+1965-01-03T00:00:00.000Z                                                                                |1964-12-31T23:00:00.000Z|1
+[1964-06-02T00:00:00.000Z, 1964-04-18T00:00:00.000Z, 1964-10-18T00:00:00.000Z, 1964-06-11T00:00:00.000Z]|1963-12-31T23:00:00.000Z|4
+[1955-01-21T00:00:00.000Z, 1955-08-20T00:00:00.000Z, 1955-08-28T00:00:00.000Z, 1955-10-04T00:00:00.000Z]|1954-12-31T23:00:00.000Z|4
+// end::bucketWithOffset-result[]
+;
+
 docsBucketMonth#[skip:-8.13.99, reason:BUCKET renamed in 8.14]
 //tag::docsBucketMonth[]
 FROM employees

docs/reference/esql/functions/kibana/definition/bucket.json

@@ -163,6 +163,17 @@ another in which the bucket size is provided directly (two parameters).
                     grouping part, or that it is invoked with the exact same expression:""",
                 file = "bucket",
                 tag = "reuseGroupingFunctionWithExpression"
+            ),
+            @Example(
+                description = """
+                    Sometimes you need to change the start value of each bucket by a given duration (similar to date histogram
+                    aggregation's <<search-aggregations-bucket-histogram-aggregation,`offset`>> parameter). To do so, you will need to
+                    take into account how the language handles expressions within the `STATS` command: if these contain functions or
+                    arithmetic operators, a virtual `EVAL` is inserted before and/or after the `STATS` command. Consequently, a double
+                    compensation is needed to adjust the bucketed date value before the aggregation and then again after. For instance,
+                    inserting a negative offset of `1 day` you would like this:""",
+                file = "bucket",
+                tag = "bucketWithOffset"
             ) }
     )
     public Bucket(