diff --git a/src/Foundation.hs b/src/Foundation.hs
index 5c39d6b86..12f430ab8 100644
--- a/src/Foundation.hs
+++ b/src/Foundation.hs
@@ -236,12 +236,12 @@ instance RenderMessage UniWorX FormMessage where
       where lang = Text.splitOn "-" $ selectLanguage' appLanguages ls
 
 instance RenderMessage UniWorX WeekDay where
-  renderMessage _ ls wDay = pack $ map fst (wDays $ getTimeLocale' ls) !! fromEnum wDay
+  renderMessage _ ls wDay = pack . fst $ wDays (getTimeLocale' ls) !! (fromEnum wDay `mod` 7)
 
 newtype ShortWeekDay = ShortWeekDay { longWeekDay :: WeekDay }
 
 instance RenderMessage UniWorX ShortWeekDay where
-  renderMessage _ ls (ShortWeekDay wDay) = pack $ map snd (wDays $ getTimeLocale' ls) !! fromEnum wDay
+  renderMessage _ ls (ShortWeekDay wDay) = pack . snd $ wDays (getTimeLocale' ls) !! (fromEnum wDay `mod` 7)
 
 -- Access Control
 newtype InvalidAuthTag = InvalidAuthTag Text