diff --git a/bin/poetry-install b/bin/poetry-install
old mode 100644
new mode 100755
diff --git a/sqrl/graphql/schema.py b/sqrl/graphql/schema.py
index 67b832e..fcdab80 100644
--- a/sqrl/graphql/schema.py
+++ b/sqrl/graphql/schema.py
@@ -214,17 +214,21 @@ class CreateTimetableMutation(graphene.Mutation):
 
     class Arguments:
         name = graphene.String(required=False, default_value=None)
+        session = graphene.String(required=False, default_value=None)
 
     timetable = graphene.Field(_TimetableObject)
     key = graphene.String()
 
     def mutate(
-        self, info: graphene.ResolveInfo, name: Optional[str] = None
+        self, info: graphene.ResolveInfo, name: Optional[str],
+        session: Optional[str] = None
     ) -> 'CreateTimetableMutation':
         """Create a timetable."""
         timetable = Timetable()
         if name is not None:
             timetable.name = name
+        if session is not None:
+            timetable.session = session
         timetable.save()
         return CreateTimetableMutation(timetable=timetable, key=timetable.key)
 
diff --git a/sqrl/models/migrations/migrate.py b/sqrl/models/migrations/migrate.py
new file mode 100644
index 0000000..de86509
--- /dev/null
+++ b/sqrl/models/migrations/migrate.py
@@ -0,0 +1,9 @@
+from sessions_and_deleted import migrate as migrate_sessions_and_deleted
+
+migrations = [migrate_sessions_and_deleted]
+
+for i, migration in enumerate(migrations):
+    try:
+        migration()
+    except:
+        print(f"Migration {i} failed or already done.")
\ No newline at end of file
diff --git a/sqrl/models/migrations/sessions_and_deleted.py b/sqrl/models/migrations/sessions_and_deleted.py
new file mode 100644
index 0000000..611ec99
--- /dev/null
+++ b/sqrl/models/migrations/sessions_and_deleted.py
@@ -0,0 +1,18 @@
+def migrate():
+    from sqrl.models.timetable import Timetable
+    from sqrl.app import create_app
+    import time
+
+    app = create_app()
+    with app.app_context():
+        assert Timetable.objects(deleted__exists=True).count() == 0
+        assert Timetable.objects(session__exists=True).count() == 0
+
+        print('Migrating timetables...')
+        start_time = time.time()
+        Timetable.objects().update(deleted=False, session="202209", schema_version=2)
+        end_time = time.time()
+        timetables = list(Timetable.objects.all())
+        print(
+            f'Migrated {len(timetables)} timetables in {end_time - start_time} seconds.')
+        return timetables
diff --git a/sqrl/models/timetable.py b/sqrl/models/timetable.py
index cc76a62..0e2c619 100644
--- a/sqrl/models/timetable.py
+++ b/sqrl/models/timetable.py
@@ -246,3 +246,9 @@ class Timetable(db.Document):
     sections: dict[str, list[str]] = db.MapField(
         db.ListField(db.StringField()), default=dict)
     deleted: bool = db.BooleanField(default=False)
+    # Sessions have two possibilities:
+    #  - they are the normal fall–winter session
+    #  - they are the summer session
+    # Sessions are represented as a 6 character string, where the first 4 characters are the year and the last two characters are the month in which the session starts.
+    session: str = db.StringField(required=True, default='202209')
+    schema_version: int = db.IntField(required=True, default=2)