Remove deprecated `TIME_ZONE` environment variable configuration

Closes #301

babybuddy/middleware.py

@@ -104,10 +104,9 @@ class UserLanguageMiddleware:
 
 class UserTimezoneMiddleware:
     """
-    Sets the timezone based on a user specific setting that falls back on
-    `settings.TIME_ZONE`. This middleware must run after
-    `django.contrib.auth.middleware.AuthenticationMiddleware` because it uses
-    the request.user object.
+    Sets the timezone based on a user specific setting. This middleware must run after
+    `django.contrib.auth.middleware.AuthenticationMiddleware` because it uses the
+    request.user object.
     """
 
     def __init__(self, get_response):

babybuddy/settings/base.py

@@ -158,7 +158,7 @@ if REVERSE_PROXY_AUTH:
 
 USE_TZ = True
 
-TIME_ZONE = os.environ.get("TIME_ZONE") or "UTC"
+TIME_ZONE = "UTC"
 
 # Internationalization
 # https://docs.djangoproject.com/en/4.0/topics/i18n/

babybuddy/tests/tests_forms.py

@@ -222,11 +222,10 @@ class FormsTestCase(TestCase):
         page = self.c.post("/user/settings/", data=params, follow=True)
         self.assertContains(page, "Paramètres utilisateur")
 
-    @override_settings(TIME_ZONE="US/Eastern")
     def test_user_settings_timezone(self):
         self.c.login(**self.credentials)
 
-        self.assertEqual(timezone.get_default_timezone_name(), "US/Eastern")
+        self.assertEqual(timezone.get_default_timezone_name(), "UTC")
         params = self.settings_template.copy()
         params["timezone"] = "US/Pacific"
         page = self.c.post("/user/settings/", data=params, follow=True)