new core.middleware sets cookie for scroll timestamp view to local browser time, w. new corresponding tests in core.tests.UTs.test_middleware; apps.lyric.templatetags.lyric_extras determines timestamp format based on duration elapsed since timestamp; apps.bill.tests.ITs.test_views renamed, now also asserts scroll renders event body and time in columns

src/core/middleware.py

@@ -0,0 +1,29 @@
+import zoneinfo
+
+from django.utils import timezone
+
+
+class TimezoneMiddleware:
+    """Activate the user's local timezone from the ``user_tz`` cookie.
+
+    The cookie is set client-side via ``Intl.DateTimeFormat().resolvedOptions().timeZone``
+    on every page load, so it reflects the browser's OS timezone rather than
+    the server's configured TIME_ZONE.  Invalid or absent cookies fall back to
+    Django's default (UTC).
+    """
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        tz_name = request.COOKIES.get("user_tz")
+        if tz_name:
+            try:
+                timezone.activate(zoneinfo.ZoneInfo(tz_name))
+            except (zoneinfo.ZoneInfoNotFoundError, KeyError):
+                timezone.deactivate()
+        else:
+            timezone.deactivate()
+        response = self.get_response(request)
+        timezone.deactivate()
+        return response

src/core/settings.py

@@ -79,6 +79,7 @@ MIDDLEWARE = [
     'django.middleware.security.SecurityMiddleware',
     'whitenoise.middleware.WhiteNoiseMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
+    'core.middleware.TimezoneMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',

src/core/tests/unit/test_middleware.py

@@ -0,0 +1,41 @@
+from django.http import HttpResponse
+from django.test import RequestFactory, SimpleTestCase
+from django.utils import timezone
+
+from core.middleware import TimezoneMiddleware
+
+
+class TimezoneMiddlewareTest(SimpleTestCase):
+
+    def setUp(self):
+        self.factory = RequestFactory()
+        self.middleware = TimezoneMiddleware(lambda r: HttpResponse())
+
+    def test_activates_valid_timezone_from_cookie(self):
+        captured = {}
+
+        def get_response(request):
+            captured["tz"] = str(timezone.get_current_timezone())
+            return HttpResponse()
+
+        middleware = TimezoneMiddleware(get_response)
+        request = self.factory.get("/")
+        request.COOKIES["user_tz"] = "America/New_York"
+        middleware(request)
+        self.assertEqual(captured["tz"], "America/New_York")
+
+    def test_deactivates_after_response(self):
+        # Timezone activation must not leak into subsequent requests
+        request = self.factory.get("/")
+        request.COOKIES["user_tz"] = "America/New_York"
+        self.middleware(request)
+        self.assertEqual(str(timezone.get_current_timezone()), "UTC")
+
+    def test_invalid_timezone_cookie_does_not_raise(self):
+        request = self.factory.get("/")
+        request.COOKIES["user_tz"] = "Not/ATimezone"
+        self.middleware(request)  # must not raise
+
+    def test_missing_cookie_does_not_raise(self):
+        request = self.factory.get("/")
+        self.middleware(request)  # must not raise