diff --git a/app/controllers/admin/conferences_controller.rb b/app/controllers/admin/conferences_controller.rb
index d8c101d1..8f8f2959 100644
--- a/app/controllers/admin/conferences_controller.rb
+++ b/app/controllers/admin/conferences_controller.rb
@@ -193,6 +193,7 @@ module Admin
     def edit
       @conferences = Conference.all
       @date_string = date_string(@conference.start_date, @conference.end_date)
+      @affected_event_count = @conference.program.events.scheduled(@conference.program.selected_schedule_id).count
       respond_to do |format|
         format.html
         format.json { render json: @conference.to_json }
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index f77d7963..b5e2892e 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -163,6 +163,12 @@ module ApplicationHelper
     end
   end
 
+  def rescheduling_hint(affected_event_count)
+    if affected_event_count > 0
+      "You have #{affected_event_count} scheduled #{'event'.pluralize(affected_event_count)}. Changing the conference hours will unschedule those scheduled outside the conference hours."
+    end
+  end
+
   ##
   # ====Gets
   # a conference object
diff --git a/app/views/admin/conferences/edit.html.haml b/app/views/admin/conferences/edit.html.haml
index b14fd7bb..ac90610d 100644
--- a/app/views/admin/conferences/edit.html.haml
+++ b/app/views/admin/conferences/edit.html.haml
@@ -22,8 +22,8 @@
         = f.input :timezone, as: :time_zone, hint: 'The conference time zone'
         = f.input :start_date, as: :string, input_html: { id: 'conference-start-datepicker', readonly: 'readonly' }
         = f.input :end_date, as: :string, input_html: { id: 'conference-end-datepicker', readonly: 'readonly' }
-        = f.input :start_hour, input_html: {size: 2, type: 'number', min: 0, max: 23}
-        = f.input :end_hour, input_html: {size: 2, type: 'number', min: 1, max: 24}
+        = f.input :start_hour, input_html: {size: 2, type: 'number', min: 0, max: 23}, hint: rescheduling_hint(@affected_event_count)
+        = f.input :end_hour, input_html: {size: 2, type: 'number', min: 1, max: 24}, hint: rescheduling_hint(@affected_event_count)
       = f.inputs name: 'Registrations' do
         = f.input :registration_limit, as: :number, in: 0..9999, hint: 'Limit the number of registrations to the conference (0 no limit). Please note that the registration limit doesn\'t apply to speakers of confirmed events (they will still be able to register even if it has been reached). You currently have ' + pluralize(@conference.registrations.count, 'registration')
       = f.inputs name: 'Booths' do