Avoid retranslating month / weekday names that Django already provides (#6301)

Co-authored-by: Thibaud Colas <thibaudcolas@gmail.com>

CHANGELOG.txt

@@ -34,6 +34,7 @@ Changelog
  * Fix: `Page.copy()` now raises an error if the page being copied is unsaved (Anton Zhyltsou)
  * Fix: `Page.copy()` now triggers a `page_published` if the copied page is live (Anton Zhyltsou)
  * Fix: The Elasticsearch `URLS` setting can now take a string on its own instead of a list (Sævar Öfjörð Magnússon)
+ * Fix: Avoid retranslating month / weekday names that Django already provides (Matt Westcott)
 
 
 2.10.2 (25.09.2020)

docs/releases/2.11.rst

@@ -48,6 +48,7 @@ Bug fixes
  * ``Page.copy()`` now raises an error if the page being copied is unsaved (Anton Zhyltsou)
  * ``Page.copy()`` now triggers a ``page_published`` if the copied page is live (Anton Zhyltsou)
  * The Elasticsearch ``URLS`` setting can now take a string on its own instead of a list (Sævar Öfjörð Magnússon)
+ * Avoid retranslating month / weekday names that Django already provides (Matt Westcott)
 
 Upgrade considerations
 ======================

wagtail/admin/localization.py

@@ -1,6 +1,7 @@
 import pytz
 
 from django.conf import settings
+from django.utils.dates import MONTHS, WEEKDAYS, WEEKDAYS_ABBR
 from django.utils.translation import gettext as _
 from django.utils.translation import gettext_lazy
 
@@ -76,38 +77,12 @@ def get_js_translation_strings():
         'VIEW_CHILD_PAGES_OF_PAGE': _('View child pages of \'{title}\''),
         'PAGE_EXPLORER': _('Page explorer'),
 
-        'MONTHS': [
-            _('January'),
-            _('February'),
-            _('March'),
-            _('April'),
-            _('May'),
-            _('June'),
-            _('July'),
-            _('August'),
-            _('September'),
-            _('October'),
-            _('November'),
-            _('December')
-        ],
-        'WEEKDAYS': [
-            _('Sunday'),
-            _('Monday'),
-            _('Tuesday'),
-            _('Wednesday'),
-            _('Thursday'),
-            _('Friday'),
-            _('Saturday')
-        ],
-        'WEEKDAYS_SHORT': [
-            _('Sun'),
-            _('Mon'),
-            _('Tue'),
-            _('Wed'),
-            _('Thu'),
-            _('Fri'),
-            _('Sat')
-        ]
+        'MONTHS': [str(m) for m in MONTHS.values()],
+
+        # Django's WEEKDAYS list begins on Monday, but ours should start on Sunday, so start
+        # counting from -1 and use modulo 7 to get an array index
+        'WEEKDAYS': [str(WEEKDAYS[d % 7]) for d in range(-1, 6)],
+        'WEEKDAYS_SHORT': [str(WEEKDAYS_ABBR[d % 7]) for d in range(-1, 6)],
     }