Correctly set timezones with amended lesson events

aleksis/apps/chronos/schema/__init__.py

+from datetime import timezone
+
 import graphene
 from graphene_django import DjangoObjectType
 from graphene_django_cud.mutations import DjangoCreateMutation, DjangoPatchMutation
@@ -71,6 +73,21 @@ class AmendLessonCreateMutation(DjangoCreateMutation):
             "comment",
         )
 
+    @classmethod
+    def handle_datetime_start(cls, value, name, info) -> int:
+        value = value.replace(tzinfo=timezone.utc)
+        return value
+
+    @classmethod
+    def handle_datetime_end(cls, value, name, info) -> int:
+        value = value.replace(tzinfo=timezone.utc)
+        return value
+
+    @classmethod
+    def before_save(cls, root, info, input, obj):
+        obj.timezone = obj.amends.timezone
+        return obj
+
 
 class AmendLessonPatchMutation(DjangoPatchMutation):
     class Meta:
@@ -78,6 +95,21 @@ class AmendLessonPatchMutation(DjangoPatchMutation):
         permissions = ("chronos.edit_substitution_rule",)
         only_fields = ("subject", "teachers", "groups", "rooms", "cancelled", "comment")
 
+    @classmethod
+    def handle_datetime_start(cls, value, name, info) -> int:
+        value = value.replace(tzinfo=timezone.utc)
+        return value
+
+    @classmethod
+    def handle_datetime_end(cls, value, name, info) -> int:
+        value = value.replace(tzinfo=timezone.utc)
+        return value
+
+    @classmethod
+    def before_save(cls, root, info, input, id, obj):
+        obj.timezone = obj.amends.timezone
+        return obj
+
 
 class TimetableType(graphene.Enum):
     TEACHER = "teacher"