The future parameter uses "has_scope".

Plus no more than 3000 events can be lister at most.

app/controllers/events_controller.rb

@@ -3,6 +3,7 @@
 class EventsController < ApplicationController
   has_scope :region, :locality, :tag, :daylimit, :year
   has_scope :near, type: :hash, using: %i[location distance]
+  has_scope :future, type: :boolean, default: true, only: [:index], if: :future?
 
   before_action :set_events, only: :index
   before_action :set_event, except: %i[index new preview_create create]
@@ -14,9 +15,9 @@ class EventsController < ApplicationController
   def index
     respond_to do |format|
       format.html
-      format.ics { @events = @events.future }
-      format.json { @events = @events.future }
-      format.rss { @events = filter_for_rss }
+      format.ics
+      format.json
+      format.rss
       format.xml
     end
   end
@@ -83,7 +84,9 @@ class EventsController < ApplicationController
   private
 
   def set_events
-    @events = apply_scopes Event.moderated
+    # The 3000 limit is purely arbitrary...
+    @events = apply_scopes Event.moderated.order('id desc')
+                                .limit(params[:format] == 'rss' ? 20 : 3000)
   end
 
   # Use callbacks to share common setup or constraints between actions
@@ -110,14 +113,6 @@ class EventsController < ApplicationController
                   :locality, :url, :contact, :submitter, :tag_list
   end
 
-  def filter_for_rss
-    if params[:future] == 'false'
-      @events.order 'id desc'
-    else
-      @events.future.order('id desc').limit 20
-    end
-  end
-
   def locked
     redirect_to edit_event_url(@event, secret: @event.secret),
                 alert: t('staleObjectError')
@@ -128,4 +123,10 @@ class EventsController < ApplicationController
     redirect_to :root, alert: t(:forbidden, scope: %i[events edit]) \
       unless params[:secret] == @event.secret
   end
+
+  # Should the future scope be applied?
+  # Only on non html pages...
+  def future?
+    params[:format].present? && params[:format] != 'html'
+  end
 end