Update date type

app/graphql/types/date.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Types
+  class Date < Types::BaseScalar
+    graphql_name "Date"
+    description "An ISO 8601-encoded date"
+
+    def self.coerce_input(value, _context)
+      begin
+        ::Date.iso8601(value.to_s)
+      rescue ArgumentError
+        raise GraphQL::CoercionError, "cannot coerce `#{value.inspect}` to Date"
+      end
+    end
+
+    def self.coerce_result(value, _context)
+      value
+    end
+  end
+end

app/graphql/types/goal_type.rb

@@ -11,7 +11,7 @@ class GoalType < BaseObject
     field :amount, Int,
           null: false,
           description: 'The amount of kudos that is required to reach the goal'
-    field :achieved_on,  GraphQL::Types::ISO8601DateTime,
+    field :achieved_on,  Types::Date,
           null: true,
           description: 'The date the goal is achieved'
     field :kudos_meter, Types::KudosMeterType,