diff --git a/app/controllers/admin/conferences_controller.rb b/app/controllers/admin/conferences_controller.rb
index e4309b7a..84f92838 100644
--- a/app/controllers/admin/conferences_controller.rb
+++ b/app/controllers/admin/conferences_controller.rb
@@ -82,6 +82,7 @@ module Admin
       short_title = @conference.short_title
       @conference.assign_attributes(conference_params)
       send_mail_on_conf_update = @conference.notify_on_dates_changed?
+      delete_event_schedules if @conference.start_hour_changed? || @conference.end_hour_changed?
 
       if @conference.update_attributes(conference_params)
         ConferenceDateUpdateMailJob.perform_later(@conference) if send_mail_on_conf_update
@@ -188,5 +189,14 @@ module Admin
                                          :targets, :targets_attributes,
                                          :campaigns, :campaigns_attributes, :registration_limit)
     end
+
+    def delete_event_schedules
+      event_schedules = EventSchedule.select do |e|
+        e.start_time.strftime('%H').to_i < @conference.start_hour ||
+        e.end_time.strftime('%H').to_i > @conference.end_hour ||
+        (e.end_time.strftime('%H').to_i == @conference.end_hour && e.end_time.strftime('%M').to_i > 0)
+      end
+      event_schedules.each(&:destroy)
+    end
   end
 end