diff --git a/src/pretix/presale/views/organizer.py b/src/pretix/presale/views/organizer.py
index af56eb5f80..1a5d96ee9a 100644
--- a/src/pretix/presale/views/organizer.py
+++ b/src/pretix/presale/views/organizer.py
@@ -225,7 +225,7 @@ class EventListMixin:
     def _set_month_year(self):
         if 'date' in self.request.GET:
             try:
-                date = dateutil.parser.parse(self.request.GET.get('date')).date()
+                date = dateutil.parser.isoparse(self.request.GET.get('date')).date()
             except ValueError:
                 date = now().date()
             self.year = date.year
diff --git a/src/tests/presale/test_event.py b/src/tests/presale/test_event.py
index 89a46658b6..d3e99a20f9 100644
--- a/src/tests/presale/test_event.py
+++ b/src/tests/presale/test_event.py
@@ -314,7 +314,7 @@ class ItemDisplayTest(EventTestMixin, SoupTest):
         resp = self.client.get('/%s/%s/' % (self.orga.slug, self.event.slug))
         self.assertIn("Foo SE2", resp.rendered_content)
         self.assertNotIn("Foo SE1", resp.rendered_content)
-        resp = self.client.get('/%s/%s/?date=%d-%d' % (self.orga.slug, self.event.slug, se1.date_from.year, se1.date_from.month))
+        resp = self.client.get('/%s/%s/?date=%d-%02d' % (self.orga.slug, self.event.slug, se1.date_from.year, se1.date_from.month))
         self.assertIn("Foo SE1", resp.rendered_content)
         self.assertNotIn("Foo SE2", resp.rendered_content)