README.md in fluent-plugin-bigquery-0.2.12 vs README.md in fluent-plugin-bigquery-0.2.13

@@ -218,11 +218,21 @@
   
   ...
 </match>
 ```
 
-Note that the timestamp of logs and the date in the table id do not always match,
-because there is a time lag between collection and transmission of logs.
+The format can be suffixed with attribute name.
+
+```apache
+<match dummy>
+  ...
+  table   accesslog_%Y_%m@timestamp
+  ...
+</match>
+```
+
+If attribute name is given, the time to be used for formatting is value of each row.
+The value for the time should be a UNIX time.
 
 ### Dynamic table creating
 
 When `auto_create_table` is set to `true`, try to create the table using BigQuery API when insertion failed with code=404 "Not Found: Table ...".
 Next retry of insertion is expected to be success.