Fix error when rendering dates for events

They were coming out as `%s`.

spectator/events/templatetags/spectator_events.py

@@ -69,7 +69,7 @@ def display_date(d):
     stamp = d.strftime("%Y-%m-%d")
     visible_date = d.strftime(app_settings.DATE_FORMAT)
 
-    return format_html('<time datetime="%s">%s</time>', stamp, visible_date)
+    return format_html('<time datetime="{}">{}</time>', stamp, visible_date)
 
 
 @register.inclusion_tag("spectator_events/includes/event_list_tabs.html")

tests/events/test_templatetags.py

@@ -1,3 +1,5 @@
+from datetime import datetime, timezone
+
 from django.test import TestCase
 
 from spectator.core.factories import IndividualCreatorFactory
@@ -16,6 +18,7 @@
     annual_event_counts,
     day_events,
     day_events_card,
+    display_date,
     event_list_tabs,
     events_years,
     events_years_card,
@@ -58,6 +61,20 @@ def test_kind(self):
         self.assertEqual(qs[1], {"year": make_date("2018-01-01"), "total": 1})
 
 
+class DisplayDateTestCase(TestCase):
+    def test_date(self):
+        d = make_date("2023-12-09")
+        self.assertEqual(
+            display_date(d), '<time datetime="2023-12-09">9 Dec 2023</time>'
+        )
+
+    def test_datetime(self):
+        dt = datetime(2023, 12, 9, 13, 30, 00).astimezone(timezone.utc)
+        self.assertEqual(
+            display_date(dt), '<time datetime="2023-12-09">9 Dec 2023</time>'
+        )
+
+
 class EventListTabsTestCase(TestCase):
     def test_result(self):
         counts = {"all": 30, "gig": 12, "movie": 18}