format in_tail path with the specified timezone

lib/fluent/plugin/in_tail.rb

@@ -96,6 +96,8 @@ def initialize
     config_param :skip_refresh_on_startup, :bool, default: false
     desc 'Ignore repeated permission error logs'
     config_param :ignore_repeated_permission_error, :bool, default: false
+    desc 'Format path with the specified timezone'
+    config_param :timezone, :string, default: nil
 
     config_section :parse, required: false, multi: true, init: true, param_name: :parser_configs do
       config_argument :usage, :string, default: 'in_tail_parser'
@@ -129,6 +131,10 @@ def configure(conf)
       if @paths.empty?
         raise Fluent::ConfigError, "tail: 'path' parameter is required on tail input"
       end
+      if @timezone
+        Fluent::Timezone.validate!(@timezone)
+        @path_formatters = @paths.map{|path| [path, Fluent::Timezone.formatter(@timezone, path)]}.to_h
+      end
 
       # TODO: Use plugin_root_dir and storage plugin to store positions if available
       if @pos_file
@@ -229,7 +235,11 @@ def expand_paths
       paths = []
 
       @paths.each { |path|
-        path = date.strftime(path)
+        path = if @timezone
+                 @path_formatters[path].call(date)
+               else
+                 date.strftime(path)
+               end
         if path.include?('*')
           paths += Dir.glob(path).select { |p|
             begin