Merge pull request #21354 from yui-knk/fix/migration_file_timestamp

[ci skip] Fix migration file's timestamp

activerecord/lib/active_record/migration.rb

@@ -459,7 +459,7 @@ def initialize(name = self.class.name, version = nil)
     # Or equivalently, if +TenderloveMigration+ is defined as in the
     # documentation for Migration:
     #
-    #   require_relative '2012121212_tenderlove_migration'
+    #   require_relative '20121212123456_tenderlove_migration'
     #
     #   class FixupTLMigration < ActiveRecord::Migration
     #     def change

guides/source/active_record_migrations.md

@@ -652,7 +652,7 @@ can't be done.
 You can use Active Record's ability to rollback migrations using the `revert` method:
 
 ```ruby
-require_relative '2012121212_example_migration'
+require_relative '20121212123456_example_migration'
 
 class FixupExampleMigration < ActiveRecord::Migration
   def change