diff --git a/aleksis/apps/chronos/form_extensions.py b/aleksis/apps/chronos/form_extensions.py
new file mode 100644
index 0000000000000000000000000000000000000000..9cb3685319279e96401f373f97fa9e322fd0885c
--- /dev/null
+++ b/aleksis/apps/chronos/form_extensions.py
@@ -0,0 +1,8 @@
+from django.utils.translation import gettext as _
+
+from material import Fieldset
+
+from aleksis.core.forms import AnnouncementForm, EditGroupForm
+
+AnnouncementForm.add_node_to_layout(Fieldset(_("Options for timetables"), "show_in_timetables"))
+EditGroupForm.add_node_to_layout(Fieldset(_("Optional data for timetables"), "subject_id"))
diff --git a/aleksis/apps/chronos/forms.py b/aleksis/apps/chronos/forms.py
index b628c2d5840edc4acf2fe555427f1d4fa70ce66d..77f870d2ef2057b6d78f12926223ec7bdbd0c08c 100644
--- a/aleksis/apps/chronos/forms.py
+++ b/aleksis/apps/chronos/forms.py
@@ -4,8 +4,6 @@ from django.utils.translation import gettext_lazy as _
 from django_select2.forms import ModelSelect2MultipleWidget
 from material import Fieldset, Layout
 
-from aleksis.core.forms import AnnouncementForm
-
 from .models import AutomaticPlan, LessonSubstitution
 
 
@@ -26,9 +24,6 @@ class LessonSubstitutionForm(forms.ModelForm):
         }
 
 
-AnnouncementForm.add_node_to_layout(Fieldset(_("Options for timetables"), "show_in_timetables"))
-
-
 class AutomaticPlanForm(forms.ModelForm):
     layout = Layout("slug", "name", "number_of_days", "show_header_box")