diff --git a/aleksis/apps/chronos/form_extensions.py b/aleksis/apps/chronos/form_extensions.py
deleted file mode 100644
index 9cb3685319279e96401f373f97fa9e322fd0885c..0000000000000000000000000000000000000000
--- a/aleksis/apps/chronos/form_extensions.py
+++ /dev/null
@@ -1,8 +0,0 @@
-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/model_extensions.py b/aleksis/apps/chronos/model_extensions.py
index 1cbe2eca074d4e42c5ac9e558999191c652787f8..06e7a1f41cf3c83065d84b4712c86712cf9d3421 100644
--- a/aleksis/apps/chronos/model_extensions.py
+++ b/aleksis/apps/chronos/model_extensions.py
@@ -4,7 +4,6 @@ from typing import Optional, Union
 from django.dispatch import receiver
 from django.utils.translation import gettext_lazy as _
 
-from jsonstore import BooleanField
 from reversion.models import Revision
 
 from aleksis.core.models import Announcement, Group, Person
@@ -138,11 +137,6 @@ def for_timetables(cls):
 
 
 Announcement.class_method(for_timetables)
-Announcement.field(
-    show_in_timetables=BooleanField(verbose_name=_("Show announcement in timetable views?"))
-)
-
-Group.foreign_key("subject", Subject, related_name="groups")
 
 # Dynamically add extra permissions to Group and Person models in core
 # Note: requires migrate afterwards