Another Day instance removed

servant-examples/tutorial/T1.hs

@@ -17,11 +17,6 @@ data User = User
   , registration_date :: Day
   } deriving (Eq, Show, Generic)
 
--- orphan ToJSON instance for Day. necessary to derive one for User
-instance ToJSON Day where
-  -- display a day in YYYY-mm-dd format
-  toJSON d = toJSON (showGregorian d)
-
 instance ToJSON User
 
 type UserAPI = "users" :> Get '[JSON] [User]