diff --git a/__tests__/new.ts b/__tests__/new.ts
index 886f2e49f158..e2ff220c5d6b 100644
--- a/__tests__/new.ts
+++ b/__tests__/new.ts
@@ -1,5 +1,5 @@
-import { Temporal } from '@js-temporal/polyfill';
 import React, { createContext, useContext } from 'react';
+import { Temporal } from 'temporal-polyfill';
 
 import {
   Endpoint,
diff --git a/docs/rest/api/schema.md b/docs/rest/api/schema.md
index dbbebc8f9812..c0fcade20249 100644
--- a/docs/rest/api/schema.md
+++ b/docs/rest/api/schema.md
@@ -46,7 +46,7 @@ We have two nested [entity](./Entity.md) types within our `article`: `users` and
 
 ```typescript
 import { schema, Entity } from '@data-client/endpoint';
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 class User extends Entity {
   id = '';
@@ -79,7 +79,7 @@ class Article extends Entity {
 
 ```javascript
 import { schema, Entity } from '@data-client/endpoint';
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 class User extends Entity { }
 
diff --git a/examples/github-app/package.json b/examples/github-app/package.json
index 4f9981973580..198c5dc1a103 100644
--- a/examples/github-app/package.json
+++ b/examples/github-app/package.json
@@ -58,7 +58,7 @@
     "@data-client/img": "0.15.0",
     "@data-client/react": "0.15.7",
     "@data-client/rest": "0.15.7",
-    "@js-temporal/polyfill": "^0.5.1",
+    "temporal-polyfill": "^0.3.0",
     "antd": "6.3.3",
     "core-js": "^3.48.0",
     "history": "^5.3.0",
diff --git a/examples/github-app/src/components/human.ts b/examples/github-app/src/components/human.ts
index 961ade3d419f..44f24d3d0460 100644
--- a/examples/github-app/src/components/human.ts
+++ b/examples/github-app/src/components/human.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 export function humanTime(date: Temporal.Instant, language: string) {
   const REL = new Intl.RelativeTimeFormat(language, {
diff --git a/examples/github-app/src/pages/IssueDetail/CommentInline.tsx b/examples/github-app/src/pages/IssueDetail/CommentInline.tsx
index 8b46c088fdc7..2fe8492d4e4b 100644
--- a/examples/github-app/src/pages/IssueDetail/CommentInline.tsx
+++ b/examples/github-app/src/pages/IssueDetail/CommentInline.tsx
@@ -2,7 +2,6 @@ import { useNavigator } from '@anansi/core';
 import { Link, useRoutes } from '@anansi/router';
 import { EllipsisOutlined } from '@ant-design/icons';
 import { useCache, useController } from '@data-client/react';
-import { Intl } from '@js-temporal/polyfill';
 import { css } from '@linaria/core';
 import { Card, Avatar, Button, Tag, Popover } from 'antd';
 import React, { memo, useCallback, useState } from 'react';
@@ -10,6 +9,7 @@ import Markdown from 'react-markdown';
 import rehypeHighlight from 'rehype-highlight';
 import remarkGfm from 'remark-gfm';
 import remarkRemoveComments from 'remark-remove-comments';
+import { Intl } from 'temporal-polyfill';
 
 import FlexRow from '@/components/FlexRow';
 import { CommentResource, Comment } from '@/resources/Comment';
diff --git a/examples/github-app/src/pages/ProfileDetail/UserEvents.tsx b/examples/github-app/src/pages/ProfileDetail/UserEvents.tsx
index 5c9f03801a2d..5f3d6d1add85 100644
--- a/examples/github-app/src/pages/ProfileDetail/UserEvents.tsx
+++ b/examples/github-app/src/pages/ProfileDetail/UserEvents.tsx
@@ -2,10 +2,10 @@ import { useNavigator } from '@anansi/core';
 import { Link } from '@anansi/router';
 import { BranchesOutlined, PullRequestOutlined } from '@ant-design/icons';
 import { useSuspense } from '@data-client/react';
-import { Intl } from '@js-temporal/polyfill';
 import { Timeline, Typography, Divider } from 'antd';
 import { groupBy } from 'lodash';
 import { useMemo } from 'react';
+import { Intl } from 'temporal-polyfill';
 
 import {
   EventResource,
diff --git a/examples/github-app/src/pages/ProfileDetail/index.tsx b/examples/github-app/src/pages/ProfileDetail/index.tsx
index e21cf279d6a6..31646cc36278 100644
--- a/examples/github-app/src/pages/ProfileDetail/index.tsx
+++ b/examples/github-app/src/pages/ProfileDetail/index.tsx
@@ -1,8 +1,8 @@
 import { useNavigator } from '@anansi/core';
 import { useSuspense } from '@data-client/react';
-import { Intl } from '@js-temporal/polyfill';
 import { Card, Layout } from 'antd';
 import Markdown from 'react-markdown';
+import { Intl } from 'temporal-polyfill';
 
 import { UserResource } from '@/resources/User';
 
diff --git a/examples/github-app/src/resources/Comment.ts b/examples/github-app/src/resources/Comment.ts
index 2247b39979ab..fa56ded4e348 100644
--- a/examples/github-app/src/resources/Comment.ts
+++ b/examples/github-app/src/resources/Comment.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { GithubEntity, githubResource } from './Base';
 import { User } from './User';
diff --git a/examples/github-app/src/resources/Event.tsx b/examples/github-app/src/resources/Event.tsx
index efc6ca2c5dd5..1ed58f4a867b 100644
--- a/examples/github-app/src/resources/Event.tsx
+++ b/examples/github-app/src/resources/Event.tsx
@@ -7,8 +7,8 @@ import {
   ForkOutlined,
 } from '@ant-design/icons';
 import { schema } from '@data-client/rest';
-import { Temporal } from '@js-temporal/polyfill';
 import type { JSX } from 'react';
+import { Temporal } from 'temporal-polyfill';
 
 import { githubResource, GithubEntity } from './Base';
 import { Issue } from './Issue';
diff --git a/examples/github-app/src/resources/Issue.tsx b/examples/github-app/src/resources/Issue.tsx
index a00e3da16b9d..0e2b98a453a2 100644
--- a/examples/github-app/src/resources/Issue.tsx
+++ b/examples/github-app/src/resources/Issue.tsx
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { GithubEntity, githubResource } from './Base';
 import { Label } from './Label';
diff --git a/examples/github-app/src/resources/Pull.ts b/examples/github-app/src/resources/Pull.ts
index 146990ed92f4..cb6995621552 100644
--- a/examples/github-app/src/resources/Pull.ts
+++ b/examples/github-app/src/resources/Pull.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { GithubEntity, githubResource } from './Base';
 import { Label } from './Label';
diff --git a/examples/github-app/src/resources/Reaction.tsx b/examples/github-app/src/resources/Reaction.tsx
index 72b73ca51b44..a9dd0e655e69 100644
--- a/examples/github-app/src/resources/Reaction.tsx
+++ b/examples/github-app/src/resources/Reaction.tsx
@@ -1,5 +1,5 @@
 import { HeartOutlined } from '@ant-design/icons';
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { githubResource, GithubEntity } from './Base';
 import PreviewEndpoint from './PreviewEndpoint';
diff --git a/examples/github-app/src/resources/Repository.tsx b/examples/github-app/src/resources/Repository.tsx
index 6129efd5a7d6..b089693de019 100644
--- a/examples/github-app/src/resources/Repository.tsx
+++ b/examples/github-app/src/resources/Repository.tsx
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { GithubEntity, githubResource, GithubGqlEndpoint } from './Base';
 
diff --git a/examples/github-app/src/resources/Review.ts b/examples/github-app/src/resources/Review.ts
index 477c07a2a076..8c882c325c44 100644
--- a/examples/github-app/src/resources/Review.ts
+++ b/examples/github-app/src/resources/Review.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { GithubEntity } from './Base';
 
diff --git a/examples/github-app/src/resources/User.ts b/examples/github-app/src/resources/User.ts
index f4528dceb74e..c0fde1e2e2a8 100644
--- a/examples/github-app/src/resources/User.ts
+++ b/examples/github-app/src/resources/User.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { githubResource, GithubEndpoint, GithubEntity } from './Base';
 
diff --git a/package.json b/package.json
index a4c789f705c9..5a4500b6a5fe 100644
--- a/package.json
+++ b/package.json
@@ -69,7 +69,6 @@
     "@data-client/react": "workspace:*",
     "@data-client/rest": "workspace:*",
     "@data-client/test": "workspace:*",
-    "@js-temporal/polyfill": "^0.5.0",
     "@react-navigation/native": "^7.0.0",
     "@react-navigation/native-stack": "^7.0.0",
     "@testing-library/dom": "^10.4.0",
@@ -103,6 +102,7 @@
     "react-test-renderer": "19.2.3",
     "rimraf": "^6.0.0",
     "rollup": "4.59.0",
+    "temporal-polyfill": "^0.3.0",
     "typescript": "6.0.2",
     "whatwg-fetch": "3.0.0"
   },
diff --git a/packages/endpoint/package.json b/packages/endpoint/package.json
index 7666b3bd9809..0613b4575552 100644
--- a/packages/endpoint/package.json
+++ b/packages/endpoint/package.json
@@ -139,11 +139,11 @@
     "@anansi/browserslist-config": "^1.4.2",
     "@data-client/core": "workspace:*",
     "@data-client/normalizr": "workspace:*",
-    "@js-temporal/polyfill": "^0.5.0",
     "@types/jest": "30.0.0",
     "@types/node": "^24.0.0",
     "immutable": "5.1.5",
     "nock": "13.3.1",
-    "rollup-plugins": "workspace:*"
+    "rollup-plugins": "workspace:*",
+    "temporal-polyfill": "^0.3.0"
   }
 }
diff --git a/packages/endpoint/src/__tests__/validateRequired.test.ts b/packages/endpoint/src/__tests__/validateRequired.test.ts
index 89a0d4733805..8fe42332ba99 100644
--- a/packages/endpoint/src/__tests__/validateRequired.test.ts
+++ b/packages/endpoint/src/__tests__/validateRequired.test.ts
@@ -1,7 +1,7 @@
 // eslint-env jest
 import { jest, describe, beforeAll, afterAll, it, expect } from '@jest/globals';
-import { Temporal } from '@js-temporal/polyfill';
 import { IDEntity } from '__tests__/new';
+import { Temporal } from 'temporal-polyfill';
 
 import SimpleMemoCache from '../schemas/__tests__/denormalize';
 import Entity from '../schemas/Entity';
diff --git a/packages/endpoint/src/schemas/__tests__/Entity.test.ts b/packages/endpoint/src/schemas/__tests__/Entity.test.ts
index 5e245be2847d..15322175199f 100644
--- a/packages/endpoint/src/schemas/__tests__/Entity.test.ts
+++ b/packages/endpoint/src/schemas/__tests__/Entity.test.ts
@@ -1,8 +1,8 @@
 import { normalize, INVALID } from '@data-client/normalizr';
 import { denormalize as plainDenormalize } from '@data-client/normalizr';
 import { denormalize as immDenormalize } from '@data-client/normalizr/imm';
-import { Temporal } from '@js-temporal/polyfill';
 import { IDEntity } from '__tests__/new';
+import { Temporal } from 'temporal-polyfill';
 
 import { SimpleMemoCache, fromJSEntities } from './denormalize';
 import { AbstractInstanceType } from '../../';
diff --git a/packages/endpoint/src/schemas/__tests__/EntityMixin.test.ts b/packages/endpoint/src/schemas/__tests__/EntityMixin.test.ts
index 1636ac9a59a9..fc7b67448b35 100644
--- a/packages/endpoint/src/schemas/__tests__/EntityMixin.test.ts
+++ b/packages/endpoint/src/schemas/__tests__/EntityMixin.test.ts
@@ -2,7 +2,7 @@
 import { normalize, INVALID } from '@data-client/normalizr';
 import { denormalize as plainDenormalize } from '@data-client/normalizr';
 import { denormalize as immDenormalize } from '@data-client/normalizr/imm';
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { SimpleMemoCache, fromJSEntities } from './denormalize';
 import { schema, EntityMixin, Values } from '../..';
diff --git a/packages/endpoint/src/schemas/__tests__/Object.test.js b/packages/endpoint/src/schemas/__tests__/Object.test.js
index 2b9faedde149..a3ceac86dda0 100644
--- a/packages/endpoint/src/schemas/__tests__/Object.test.js
+++ b/packages/endpoint/src/schemas/__tests__/Object.test.js
@@ -4,9 +4,9 @@ import {
   denormalize as plainDenormalize,
 } from '@data-client/normalizr';
 import { denormalize as immDenormalize } from '@data-client/normalizr/imm';
-import { Temporal } from '@js-temporal/polyfill';
 import { IDEntity } from '__tests__/new';
 import { fromJS } from 'immutable';
+import { Temporal } from 'temporal-polyfill';
 
 import { fromJSEntities } from './denormalize';
 import { schema } from '../../';
diff --git a/packages/endpoint/src/schemas/__tests__/Serializable.test.ts b/packages/endpoint/src/schemas/__tests__/Serializable.test.ts
index 6d2c231d6560..711be8cd396b 100644
--- a/packages/endpoint/src/schemas/__tests__/Serializable.test.ts
+++ b/packages/endpoint/src/schemas/__tests__/Serializable.test.ts
@@ -1,7 +1,7 @@
 // eslint-env jest
 import { normalize } from '@data-client/normalizr';
-import { Temporal } from '@js-temporal/polyfill';
 import { IDEntity } from '__tests__/new';
+import { Temporal } from 'temporal-polyfill';
 
 import SimpleMemoCache from './denormalize';
 
diff --git a/packages/normalizr/README.md b/packages/normalizr/README.md
index 757ea41fd79d..f7acaf66b656 100644
--- a/packages/normalizr/README.md
+++ b/packages/normalizr/README.md
@@ -88,7 +88,7 @@ We have two [nested](https://dataclient.io/rest/guides/relational-data) [entity]
 
 ```js
 import { schema, Entity } from '@data-client/endpoint';
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 // Define a users schema
 class User extends Entity {}
diff --git a/packages/normalizr/package.json b/packages/normalizr/package.json
index 1ecf9219fa72..d343d8d5a60d 100644
--- a/packages/normalizr/package.json
+++ b/packages/normalizr/package.json
@@ -127,10 +127,10 @@
   "devDependencies": {
     "@anansi/browserslist-config": "^1.4.2",
     "@data-client/endpoint": "workspace:*",
-    "@js-temporal/polyfill": "^0.5.0",
     "@types/jest": "30.0.0",
     "@types/node": "^24.0.0",
     "immutable": "5.1.5",
-    "rollup-plugins": "workspace:*"
+    "rollup-plugins": "workspace:*",
+    "temporal-polyfill": "^0.3.0"
   }
 }
diff --git a/packages/normalizr/src/__tests__/WeakDependencyMap.test.ts b/packages/normalizr/src/__tests__/WeakDependencyMap.test.ts
index 3273cd578363..53150894b169 100644
--- a/packages/normalizr/src/__tests__/WeakDependencyMap.test.ts
+++ b/packages/normalizr/src/__tests__/WeakDependencyMap.test.ts
@@ -1,4 +1,4 @@
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 import { EntityPath } from '../interface';
 import { MemoPolicy } from '../memo/Policy';
diff --git a/packages/react/package.json b/packages/react/package.json
index 5faec1f06655..00576fc88d14 100644
--- a/packages/react/package.json
+++ b/packages/react/package.json
@@ -200,7 +200,6 @@
     "@data-client/rest": "workspace:*",
     "@data-client/test": "workspace:*",
     "@jest/globals": "^30.0.0",
-    "@js-temporal/polyfill": "^0.5.0",
     "@react-navigation/native": "^7.0.0",
     "@react-navigation/native-stack": "^7.2.0",
     "@testing-library/dom": "^10.4.0",
@@ -220,6 +219,7 @@
     "react-native-safe-area-context": "^5.0.0",
     "react-native-screens": "^4.1.0",
     "react-test-renderer": "^19.0.0",
-    "rollup-plugins": "workspace:*"
+    "rollup-plugins": "workspace:*",
+    "temporal-polyfill": "^0.3.0"
   }
 }
diff --git a/packages/react/src/__tests__/useFetch-use.web.tsx b/packages/react/src/__tests__/useFetch-use.web.tsx
index 7f5fa4eb515b..04104ca6e0e3 100644
--- a/packages/react/src/__tests__/useFetch-use.web.tsx
+++ b/packages/react/src/__tests__/useFetch-use.web.tsx
@@ -10,7 +10,6 @@ import { Collection, Values } from '@data-client/endpoint';
 import { normalize } from '@data-client/normalizr';
 import { DataProvider } from '@data-client/react';
 import { jest } from '@jest/globals';
-import { Temporal } from '@js-temporal/polyfill';
 import { render } from '@testing-library/react';
 import {
   CoolerArticleResource,
@@ -32,6 +31,7 @@ import { createEntityMeta } from '__tests__/utils';
 import nock from 'nock';
 import { use } from 'react';
 import React, { Suspense } from 'react';
+import { Temporal } from 'temporal-polyfill';
 
 // relative imports to avoid circular dependency in tsconfig references
 import { useController, ControllerContext, StateContext } from '..';
diff --git a/packages/react/src/hooks/__tests__/useSuspense.native.tsx b/packages/react/src/hooks/__tests__/useSuspense.native.tsx
index 704a9107d6ff..7631c4ee97df 100644
--- a/packages/react/src/hooks/__tests__/useSuspense.native.tsx
+++ b/packages/react/src/hooks/__tests__/useSuspense.native.tsx
@@ -15,7 +15,6 @@ import {
   MockResolver,
 } from '@data-client/test';
 import { jest } from '@jest/globals';
-import { Temporal } from '@js-temporal/polyfill';
 import { NavigationContainer } from '@react-navigation/native';
 import { createNativeStackNavigator } from '@react-navigation/native-stack';
 import { render, act, screen } from '@testing-library/react-native';
@@ -38,6 +37,7 @@ import nock from 'nock';
 import React, { Suspense } from 'react';
 import { Text, View } from 'react-native';
 import { InteractionManager } from 'react-native';
+import { Temporal } from 'temporal-polyfill';
 
 // relative imports to avoid circular dependency in tsconfig references
 import {
diff --git a/packages/react/src/hooks/__tests__/useSuspense.web.tsx b/packages/react/src/hooks/__tests__/useSuspense.web.tsx
index dbfeb2351c17..f5055de9a367 100644
--- a/packages/react/src/hooks/__tests__/useSuspense.web.tsx
+++ b/packages/react/src/hooks/__tests__/useSuspense.web.tsx
@@ -16,7 +16,6 @@ import {
 } from '@data-client/endpoint';
 import { normalize } from '@data-client/normalizr';
 import { jest } from '@jest/globals';
-import { Temporal } from '@js-temporal/polyfill';
 import { render } from '@testing-library/react';
 import {
   CoolerArticleResource,
@@ -37,6 +36,7 @@ import {
 import { createEntityMeta } from '__tests__/utils';
 import nock from 'nock';
 import React, { Suspense } from 'react';
+import { Temporal } from 'temporal-polyfill';
 
 // relative imports to avoid circular dependency in tsconfig references
 import {
diff --git a/packages/vue/package.json b/packages/vue/package.json
index bf492f17e531..3b259beb5f62 100644
--- a/packages/vue/package.json
+++ b/packages/vue/package.json
@@ -113,7 +113,6 @@
     "@anansi/browserslist-config": "^1.4.2",
     "@data-client/rest": "workspace:*",
     "@jest/globals": "^30.0.0",
-    "@js-temporal/polyfill": "^0.5.0",
     "@types/jest": "30.0.0",
     "@types/node": "^24.0.0",
     "@vue/test-utils": "^2.4.0",
@@ -121,6 +120,7 @@
     "jest-mock": "^30.0.0",
     "nock": "13.3.1",
     "rollup-plugins": "workspace:*",
+    "temporal-polyfill": "^0.3.0",
     "vue": "^3.4.0"
   }
 }
diff --git a/scripts/copywebsitetypes.sh b/scripts/copywebsitetypes.sh
index c3744dc2969c..ec58c61dfe77 100755
--- a/scripts/copywebsitetypes.sh
+++ b/scripts/copywebsitetypes.sh
@@ -14,7 +14,7 @@ cp ./packages/react/nextjs.d.ts ./website/src/components/Playground/editor-types
 cp ./packages/react/ssr.d.ts ./website/src/components/Playground/editor-types/@data-client/react/ssr.d.ts
 cp ./packages/react/redux.d.ts ./website/src/components/Playground/editor-types/@data-client/react/redux.d.ts
 cp ./node_modules/@types/react/index.d.ts ./website/src/components/Playground/editor-types/react.d.ts
-cp ./node_modules/@js-temporal/polyfill/index.d.ts ./website/src/components/Playground/editor-types/temporal.d.ts
+cp ./node_modules/temporal-spec/index.d.ts ./website/src/components/Playground/editor-types/temporal.d.ts
 cp ./node_modules/bignumber.js/bignumber.d.ts ./website/src/components/Playground/editor-types/bignumber.d.ts
 cp ./node_modules/@types/qs/index.d.ts ./website/src/components/Playground/editor-types/qs.d.ts
 yarn run rollup --config ./scripts/rollup-plugins/uuid-types.rollup.config.js
diff --git a/website/blog/2024-01-15-v0.9-release-announcement.md b/website/blog/2024-01-15-v0.9-release-announcement.md
index fc059236a3f2..adcf4a838aa2 100644
--- a/website/blog/2024-01-15-v0.9-release-announcement.md
+++ b/website/blog/2024-01-15-v0.9-release-announcement.md
@@ -286,7 +286,7 @@ class MyEntity extends Entity {
 Alternatively, use Temporal:
 
 ```ts
-import { Temporal } from '@js-temporal/polyfill';
+import { Temporal } from 'temporal-polyfill';
 
 class MyEntity extends Entity {
   createdAt = Temporal.Instant.fromEpochSeconds(0);
diff --git a/website/package.json b/website/package.json
index 561a0b75b701..ae379f1c95b8 100644
--- a/website/package.json
+++ b/website/package.json
@@ -44,7 +44,6 @@
     "@docusaurus/preset-classic": "^3.0.1",
     "@docusaurus/theme-live-codeblock": "^3.0.1",
     "@docusaurus/theme-mermaid": "^3.0.1",
-    "@js-temporal/polyfill": "^0.5.0",
     "@mdx-js/react": "^3.1.0",
     "@monaco-editor/react": "^4.8.0-rc.0",
     "@number-flow/react": "^0.6.0",
@@ -56,6 +55,7 @@
     "react-dom": "^19.0.0",
     "react-json-tree": "0.20.0",
     "react-live": "^4.0.0",
+    "temporal-polyfill": "^0.3.0",
     "typescript": "6.0.2",
     "uuid": "^13.0.0"
   },
diff --git a/website/src/components/Playground/PreviewWithScope.tsx b/website/src/components/Playground/PreviewWithScope.tsx
index c00f4f8b92b6..2247ddb8f8e7 100644
--- a/website/src/components/Playground/PreviewWithScope.tsx
+++ b/website/src/components/Playground/PreviewWithScope.tsx
@@ -2,7 +2,6 @@ import * as graphql from '@data-client/graphql';
 import * as rhReact from '@data-client/react';
 import * as rhReactNext from '@data-client/react/next';
 import * as rest from '@data-client/rest';
-import { Temporal, Intl as PolyIntl } from '@js-temporal/polyfill';
 import BigNumber from 'bignumber.js';
 import { use } from 'react';
 import { LiveProvider } from 'react-live';
@@ -11,6 +10,7 @@ import { v4 as uuid } from 'uuid';
 import * as designSystem from './DesignSystem';
 import Preview from './Preview';
 import PreviewWrapper from './PreviewWrapper';
+import { Temporal, Intl, DateTimeFormat } from './temporal';
 import transformCode from './transformCode';
 import type { PreviewProps } from './types';
 import ResetableErrorBoundary from '../ResettableErrorBoundary';
@@ -31,11 +31,6 @@ const mockFetch = (getResponse, name, delay = 150) => {
   return fetch;
 };
 
-const Intl = {
-  ...globalThis.Intl,
-  ...PolyIntl,
-};
-
 const scope = {
   ...rhReact,
   ...rhReactNext,
@@ -49,7 +44,7 @@ const scope = {
   ResetableErrorBoundary,
   Temporal,
   Intl,
-  DateTimeFormat: PolyIntl.DateTimeFormat,
+  DateTimeFormat,
   ...designSystem,
 };
 
diff --git a/website/src/components/Playground/editor-types/temporal.d.ts b/website/src/components/Playground/editor-types/temporal.d.ts
index ac2d6be085c4..c29e54693f77 100644
--- a/website/src/components/Playground/editor-types/temporal.d.ts
+++ b/website/src/components/Playground/editor-types/temporal.d.ts
@@ -1,6 +1,10 @@
+/*
+NOTE: keep synced with all other definition files
+*/
+
 export namespace Temporal {
-  export type ComparisonResult = -1 | 0 | 1;
-  export type RoundingMode =
+  type ComparisonResult = -1 | 0 | 1;
+  type RoundingMode =
     | 'ceil'
     | 'floor'
     | 'expand'
@@ -15,7 +19,7 @@ export namespace Temporal {
    * Options for assigning fields using `with()` or entire objects with
    * `from()`.
    * */
-  export type AssignmentOptions = {
+  type AssignmentOptions = {
     /**
      * How to deal with out-of-range values
      *
@@ -26,7 +30,7 @@ export namespace Temporal {
      *
      * The default is `'constrain'`.
      */
-    overflow?: 'constrain' | 'reject';
+    overflow?: 'constrain' | 'reject' | undefined;
   };
 
   /**
@@ -34,7 +38,7 @@ export namespace Temporal {
    * objects with `Duration.from()`, and for arithmetic with
    * `Duration.prototype.add()` and `Duration.prototype.subtract()`.
    * */
-  export type DurationOptions = {
+  type DurationOptions = {
     /**
      * How to deal with out-of-range values
      *
@@ -45,13 +49,13 @@ export namespace Temporal {
      *
      * The default is `'constrain'`.
      */
-    overflow?: 'constrain' | 'balance';
+    overflow?: 'constrain' | 'balance' | undefined;
   };
 
   /**
    * Options for conversions of `Temporal.PlainDateTime` to `Temporal.Instant`
    * */
-  export type ToInstantOptions = {
+  type ToInstantOptions = {
     /**
      * Controls handling of invalid or ambiguous times caused by time zone
      * offset changes like Daylight Saving time (DST) transitions.
@@ -75,7 +79,7 @@ export namespace Temporal {
      * The default is `'compatible'`.
      *
      * */
-    disambiguation?: 'compatible' | 'earlier' | 'later' | 'reject';
+    disambiguation?: 'compatible' | 'earlier' | 'later' | 'reject' | undefined;
   };
 
   type OffsetDisambiguationOptions = {
@@ -111,17 +115,15 @@ export namespace Temporal {
      * be used to choose the correct instant. However, if the offset is used
      * then the `disambiguation` option will be ignored.
      */
-    offset?: 'use' | 'prefer' | 'ignore' | 'reject';
+    offset?: 'use' | 'prefer' | 'ignore' | 'reject' | undefined;
   };
 
-  export type ZonedDateTimeAssignmentOptions = Partial<
-    AssignmentOptions & ToInstantOptions & OffsetDisambiguationOptions
-  >;
+  type ZonedDateTimeAssignmentOptions = AssignmentOptions & ToInstantOptions & OffsetDisambiguationOptions;
 
   /**
    * Options for arithmetic operations like `add()` and `subtract()`
    * */
-  export type ArithmeticOptions = {
+  type ArithmeticOptions = {
     /**
      * Controls handling of out-of-range arithmetic results.
      *
@@ -130,19 +132,19 @@ export namespace Temporal {
      *
      * The default is `'constrain'`.
      */
-    overflow?: 'constrain' | 'reject';
+    overflow?: 'constrain' | 'reject' | undefined;
   };
 
-  export type DateUnit = 'year' | 'month' | 'week' | 'day';
-  export type TimeUnit = 'hour' | 'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond';
-  export type DateTimeUnit = DateUnit | TimeUnit;
+  type DateUnit = 'year' | 'month' | 'week' | 'day';
+  type TimeUnit = 'hour' | 'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond';
+  type DateTimeUnit = DateUnit | TimeUnit;
 
   /**
    * When the name of a unit is provided to a Temporal API as a string, it is
    * usually singular, e.g. 'day' or 'hour'. But plural unit names like 'days'
    * or 'hours' are also accepted.
    * */
-  export type PluralUnit<T extends DateTimeUnit> = {
+  type PluralUnit<T extends DateTimeUnit> = {
     year: 'years';
     month: 'months';
     week: 'weeks';
@@ -155,16 +157,16 @@ export namespace Temporal {
     nanosecond: 'nanoseconds';
   }[T];
 
-  export type LargestUnit<T extends DateTimeUnit> = 'auto' | T | PluralUnit<T>;
-  export type SmallestUnit<T extends DateTimeUnit> = T | PluralUnit<T>;
-  export type TotalUnit<T extends DateTimeUnit> = T | PluralUnit<T>;
+  type LargestUnit<T extends DateTimeUnit> = 'auto' | T | PluralUnit<T>;
+  type SmallestUnit<T extends DateTimeUnit> = T | PluralUnit<T>;
+  type TotalUnit<T extends DateTimeUnit> = T | PluralUnit<T>;
 
   /**
    * Options for outputting precision in toString() on types with seconds
    */
-  export type ToStringPrecisionOptions = {
-    fractionalSecondDigits?: 'auto' | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9;
-    smallestUnit?: SmallestUnit<'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond'>;
+  type ToStringPrecisionOptions = {
+    fractionalSecondDigits?: 'auto' | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | undefined;
+    smallestUnit?: SmallestUnit<'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond'> | undefined;
 
     /**
      * Controls how rounding is performed:
@@ -180,40 +182,36 @@ export namespace Temporal {
      *   negative infinity which is usually unexpected. For this reason, `trunc`
      *   is recommended for most use cases.
      */
-    roundingMode?: RoundingMode;
+    roundingMode?: RoundingMode | undefined;
   };
 
-  export type ShowCalendarOption = {
-    calendarName?: 'auto' | 'always' | 'never' | 'critical';
+  type ShowCalendarOption = {
+    calendarName?: 'auto' | 'always' | 'never' | 'critical' | undefined;
   };
 
-  export type CalendarTypeToStringOptions = Partial<ToStringPrecisionOptions & ShowCalendarOption>;
+  type CalendarTypeToStringOptions = ToStringPrecisionOptions & ShowCalendarOption;
 
-  export type ZonedDateTimeToStringOptions = Partial<
-    CalendarTypeToStringOptions & {
-      timeZoneName?: 'auto' | 'never' | 'critical';
-      offset?: 'auto' | 'never';
-    }
-  >;
+  type ZonedDateTimeToStringOptions = CalendarTypeToStringOptions & {
+    timeZoneName?: 'auto' | 'never' | 'critical' | undefined;
+    offset?: 'auto' | 'never' | undefined;
+  };
 
-  export type InstantToStringOptions = Partial<
-    ToStringPrecisionOptions & {
-      timeZone: TimeZoneLike;
-    }
-  >;
+  type InstantToStringOptions = ToStringPrecisionOptions & {
+    timeZone?: TimeZoneLike | undefined;
+  };
 
   /**
    * Options to control the result of `until()` and `since()` methods in
    * `Temporal` types.
    */
-  export interface DifferenceOptions<T extends DateTimeUnit> {
+  interface DifferenceOptions<T extends DateTimeUnit> {
     /**
      * The unit to round to. For example, to round to the nearest minute, use
      * `smallestUnit: 'minute'`. This property is optional for `until()` and
      * `since()`, because those methods default behavior is not to round.
      * However, the same property is required for `round()`.
      */
-    smallestUnit?: SmallestUnit<T>;
+    smallestUnit?: SmallestUnit<T> | undefined;
 
     /**
      * The largest unit to allow in the resulting `Temporal.Duration` object.
@@ -231,14 +229,14 @@ export namespace Temporal {
      * The default is always `'auto'`, though the meaning of this depends on the
      * type being used.
      */
-    largestUnit?: LargestUnit<T>;
+    largestUnit?: LargestUnit<T> | undefined;
 
     /**
      * Allows rounding to an integer number of units. For example, to round to
      * increments of a half hour, use `{ smallestUnit: 'minute',
      * roundingIncrement: 30 }`.
      */
-    roundingIncrement?: number;
+    roundingIncrement?: number | undefined;
 
     /**
      * Controls how rounding is performed:
@@ -256,7 +254,7 @@ export namespace Temporal {
      *   negative infinity which is usually unexpected. For this reason, `trunc`
      *   is recommended for most use cases.
      */
-    roundingMode?: RoundingMode;
+    roundingMode?: RoundingMode | undefined;
   }
 
   /**
@@ -266,7 +264,7 @@ export namespace Temporal {
    * properties are optional. A string is treated the same as an object whose
    * `smallestUnit` property value is that string.
    */
-  export type RoundTo<T extends DateTimeUnit> =
+  type RoundTo<T extends DateTimeUnit> =
     | SmallestUnit<T>
     | {
         /**
@@ -282,7 +280,7 @@ export namespace Temporal {
          * increments of a half hour, use `{ smallestUnit: 'minute',
          * roundingIncrement: 30 }`.
          */
-        roundingIncrement?: number;
+        roundingIncrement?: number | undefined;
 
         /**
          * Controls how rounding is performed:
@@ -298,7 +296,7 @@ export namespace Temporal {
          *   negative infinity which is usually unexpected. For this reason, `trunc`
          *   is recommended for most use cases.
          */
-        roundingMode?: RoundingMode;
+        roundingMode?: RoundingMode | undefined;
       };
 
   /**
@@ -309,7 +307,7 @@ export namespace Temporal {
    * properties are optional. A string parameter is treated the same as an
    * object whose `smallestUnit` property value is that string.
    */
-  export type DurationRoundTo =
+  type DurationRoundTo =
     | SmallestUnit<DateTimeUnit>
     | ((
         | {
@@ -340,7 +338,7 @@ export namespace Temporal {
              * If `smallestUnit` is larger, then `smallestUnit` will be used as
              * `largestUnit`, superseding a caller-supplied or default value.
              */
-            largestUnit?: LargestUnit<DateTimeUnit>;
+            largestUnit?: LargestUnit<DateTimeUnit> | undefined;
           }
         | {
             /**
@@ -349,7 +347,7 @@ export namespace Temporal {
              * required, but is optional if `largestUnit` is provided and not
              * undefined.
              */
-            smallestUnit?: SmallestUnit<DateTimeUnit>;
+            smallestUnit?: SmallestUnit<DateTimeUnit> | undefined;
 
             /**
              * The largest unit to allow in the resulting `Temporal.Duration`
@@ -378,7 +376,7 @@ export namespace Temporal {
          * to increments of a half hour, use `{ smallestUnit: 'minute',
          * roundingIncrement: 30 }`.
          */
-        roundingIncrement?: number;
+        roundingIncrement?: number | undefined;
 
         /**
          * Controls how rounding is performed:
@@ -397,7 +395,7 @@ export namespace Temporal {
          *   unexpected. For this reason, `trunc` is recommended for most "round
          *   down" use cases.
          */
-        roundingMode?: RoundingMode;
+        roundingMode?: RoundingMode | undefined;
 
         /**
          * The starting point to use for rounding and conversions when
@@ -423,13 +421,19 @@ export namespace Temporal {
          * time zone transitions and all days will be assumed to be 24 hours
          * long.
          */
-        relativeTo?: Temporal.PlainDateTime | Temporal.ZonedDateTime | PlainDateTimeLike | ZonedDateTimeLike | string;
+        relativeTo?:
+          | Temporal.PlainDateTime
+          | Temporal.ZonedDateTime
+          | PlainDateTimeLike
+          | ZonedDateTimeLike
+          | string
+          | undefined;
       });
 
   /**
    * Options to control behavior of `Duration.prototype.total()`
    */
-  export type DurationTotalOf =
+  type DurationTotalOf =
     | TotalUnit<DateTimeUnit>
     | {
         /**
@@ -459,13 +463,19 @@ export namespace Temporal {
          * this option is omitted), then the operation will ignore time zone
          * transitions and all days will be assumed to be 24 hours long.
          */
-        relativeTo?: Temporal.ZonedDateTime | Temporal.PlainDateTime | ZonedDateTimeLike | PlainDateTimeLike | string;
+        relativeTo?:
+          | Temporal.ZonedDateTime
+          | Temporal.PlainDateTime
+          | ZonedDateTimeLike
+          | PlainDateTimeLike
+          | string
+          | undefined;
       };
 
   /**
    * Options to control behavior of `Duration.compare()`
    */
-  export interface DurationArithmeticOptions {
+  interface DurationArithmeticOptions {
     /**
      * The starting point to use when variable-length units (years, months,
      * weeks depending on the calendar) are involved. This option is required if
@@ -486,32 +496,61 @@ export namespace Temporal {
      * this option is omitted), then the operation will ignore time zone
      * transitions and all days will be assumed to be 24 hours long.
      */
-    relativeTo?: Temporal.ZonedDateTime | Temporal.PlainDateTime | ZonedDateTimeLike | PlainDateTimeLike | string;
+    relativeTo?:
+      | Temporal.ZonedDateTime
+      | Temporal.PlainDateTime
+      | ZonedDateTimeLike
+      | PlainDateTimeLike
+      | string
+      | undefined;
   }
 
   /**
    * Options to control behaviour of `ZonedDateTime.prototype.getTimeZoneTransition()`
    */
-  export type TransitionDirection = 'next' | 'previous' | { direction: 'next' | 'previous' };
-
-  // Handle Intl.LocalesArgument regardless of whether the TS version has it yet
-  type LocalesArgument = ConstructorParameters<typeof Intl.DateTimeFormat>[0];
-  // Provide a quick replacement for Intl.DurationFormatOptions if not in TS
-  type DurationFormatOptions = typeof Intl extends { DurationFormat: any }
-    ? ConstructorParameters<(typeof Intl)['DurationFormat']>[1]
-    : Record<string, unknown>;
-
-  export type DurationLike = {
-    years?: number;
-    months?: number;
-    weeks?: number;
-    days?: number;
-    hours?: number;
-    minutes?: number;
-    seconds?: number;
-    milliseconds?: number;
-    microseconds?: number;
-    nanoseconds?: number;
+  type TransitionDirection = 'next' | 'previous' | { direction: 'next' | 'previous' };
+
+  type DurationLike = {
+    years?: number | undefined;
+    months?: number | undefined;
+    weeks?: number | undefined;
+    days?: number | undefined;
+    hours?: number | undefined;
+    minutes?: number | undefined;
+    seconds?: number | undefined;
+    milliseconds?: number | undefined;
+    microseconds?: number | undefined;
+    nanoseconds?: number | undefined;
+  };
+
+  /**
+   * Options for Intl.DurationFormat
+   */
+  export type DurationFormatOptions = {
+    localeMatcher?: 'lookup' | 'best fit' | undefined;
+    numberingSystem?: string | undefined;
+    style?: 'long' | 'short' | 'narrow' | 'digital' | undefined;
+    years?: 'long' | 'short' | 'narrow' | undefined;
+    yearsDisplay?: 'always' | 'auto' | undefined;
+    months?: 'long' | 'short' | 'narrow' | undefined;
+    monthsDisplay?: 'always' | 'auto' | undefined;
+    weeks?: 'long' | 'short' | 'narrow' | undefined;
+    weeksDisplay?: 'always' | 'auto' | undefined;
+    days?: 'long' | 'short' | 'narrow' | undefined;
+    daysDisplay?: 'always' | 'auto' | undefined;
+    hours?: 'long' | 'short' | 'narrow' | 'numeric' | '2-digit' | undefined;
+    hoursDisplay?: 'always' | 'auto' | undefined;
+    minutes?: 'long' | 'short' | 'narrow' | 'numeric' | '2-digit' | undefined;
+    minutesDisplay?: 'always' | 'auto' | undefined;
+    seconds?: 'long' | 'short' | 'narrow' | 'numeric' | '2-digit' | undefined;
+    secondsDisplay?: 'always' | 'auto' | undefined;
+    milliseconds?: 'long' | 'short' | 'narrow' | 'numeric' | undefined;
+    millisecondsDisplay?: 'always' | 'auto' | undefined;
+    microseconds?: 'long' | 'short' | 'narrow' | 'numeric' | undefined;
+    microsecondsDisplay?: 'always' | 'auto' | undefined;
+    nanoseconds?: 'long' | 'short' | 'narrow' | 'numeric' | undefined;
+    nanosecondsDisplay?: 'always' | 'auto' | undefined;
+    fractionalDigits?: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | undefined;
   };
 
   /**
@@ -521,7 +560,7 @@ export namespace Temporal {
    *
    * See https://tc39.es/proposal-temporal/docs/duration.html for more details.
    */
-  export class Duration {
+  class Duration {
     static from(item: Temporal.Duration | DurationLike | string): Temporal.Duration;
     static compare(
       one: Temporal.Duration | DurationLike | string,
@@ -559,7 +598,7 @@ export namespace Temporal {
     subtract(other: Temporal.Duration | DurationLike | string): Temporal.Duration;
     round(roundTo: DurationRoundTo): Temporal.Duration;
     total(totalOf: DurationTotalOf): number;
-    toLocaleString(locales?: LocalesArgument, options?: DurationFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: DurationFormatOptions): string;
     toJSON(): string;
     toString(options?: ToStringPrecisionOptions): string;
     valueOf(): never;
@@ -580,7 +619,7 @@ export namespace Temporal {
    *
    * See https://tc39.es/proposal-temporal/docs/instant.html for more details.
    */
-  export class Instant {
+  class Instant {
     static fromEpochMilliseconds(epochMilliseconds: number): Temporal.Instant;
     static fromEpochNanoseconds(epochNanoseconds: bigint): Temporal.Instant;
     static from(item: Temporal.Instant | string): Temporal.Instant;
@@ -607,7 +646,7 @@ export namespace Temporal {
       roundTo: RoundTo<'hour' | 'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond'>
     ): Temporal.Instant;
     toZonedDateTimeISO(tzLike: TimeZoneLike): Temporal.ZonedDateTime;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: InstantToStringOptions): string;
     valueOf(): never;
@@ -619,14 +658,14 @@ export namespace Temporal {
    * */
   export type CalendarLike = string | ZonedDateTime | PlainDateTime | PlainDate | PlainYearMonth | PlainMonthDay;
 
-  export type PlainDateLike = {
+  type PlainDateLike = {
     era?: string | undefined;
     eraYear?: number | undefined;
-    year?: number;
-    month?: number;
-    monthCode?: string;
-    day?: number;
-    calendar?: CalendarLike;
+    year?: number | undefined;
+    month?: number | undefined;
+    monthCode?: string | undefined;
+    day?: number | undefined;
+    calendar?: CalendarLike | undefined;
   };
 
   /**
@@ -636,9 +675,9 @@ export namespace Temporal {
    * which happens during the whole day no matter which time zone it's happening
    * in.
    *
-   * See https://tc39.es/proposal-temporal/docs/plaindate.html for more details.
+   * See https://tc39.es/proposal-temporal/docs/date.html for more details.
    */
-  export class PlainDate {
+  class PlainDate {
     static from(item: Temporal.PlainDate | PlainDateLike | string, options?: AssignmentOptions): Temporal.PlainDate;
     static compare(
       one: Temporal.PlainDate | PlainDateLike | string,
@@ -680,32 +719,32 @@ export namespace Temporal {
         | string
         | {
             timeZone: TimeZoneLike;
-            plainTime?: Temporal.PlainTime | PlainTimeLike | string;
+            plainTime?: Temporal.PlainTime | PlainTimeLike | string | undefined;
           }
     ): Temporal.ZonedDateTime;
     toPlainYearMonth(): Temporal.PlainYearMonth;
     toPlainMonthDay(): Temporal.PlainMonthDay;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: ShowCalendarOption): string;
     valueOf(): never;
     readonly [Symbol.toStringTag]: 'Temporal.PlainDate';
   }
 
-  export type PlainDateTimeLike = {
+  type PlainDateTimeLike = {
     era?: string | undefined;
     eraYear?: number | undefined;
-    year?: number;
-    month?: number;
-    monthCode?: string;
-    day?: number;
-    hour?: number;
-    minute?: number;
-    second?: number;
-    millisecond?: number;
-    microsecond?: number;
-    nanosecond?: number;
-    calendar?: CalendarLike;
+    year?: number | undefined;
+    month?: number | undefined;
+    monthCode?: string | undefined;
+    day?: number | undefined;
+    hour?: number | undefined;
+    minute?: number | undefined;
+    second?: number | undefined;
+    millisecond?: number | undefined;
+    microsecond?: number | undefined;
+    nanosecond?: number | undefined;
+    calendar?: CalendarLike | undefined;
   };
 
   /**
@@ -716,9 +755,9 @@ export namespace Temporal {
    * and `Temporal.PlainMonthDay` all carry less information and should be used when
    * complete information is not required.
    *
-   * See https://tc39.es/proposal-temporal/docs/plaindatetime.html for more details.
+   * See https://tc39.es/proposal-temporal/docs/datetime.html for more details.
    */
-  export class PlainDateTime {
+  class PlainDateTime {
     static from(
       item: Temporal.PlainDateTime | PlainDateTimeLike | string,
       options?: AssignmentOptions
@@ -788,21 +827,21 @@ export namespace Temporal {
     toZonedDateTime(tzLike: TimeZoneLike, options?: ToInstantOptions): Temporal.ZonedDateTime;
     toPlainDate(): Temporal.PlainDate;
     toPlainTime(): Temporal.PlainTime;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: CalendarTypeToStringOptions): string;
     valueOf(): never;
     readonly [Symbol.toStringTag]: 'Temporal.PlainDateTime';
   }
 
-  export type PlainMonthDayLike = {
+  type PlainMonthDayLike = {
     era?: string | undefined;
     eraYear?: number | undefined;
-    year?: number;
-    month?: number;
-    monthCode?: string;
-    day?: number;
-    calendar?: CalendarLike;
+    year?: number | undefined;
+    month?: number | undefined;
+    monthCode?: string | undefined;
+    day?: number | undefined;
+    calendar?: CalendarLike | undefined;
   };
 
   /**
@@ -810,9 +849,9 @@ export namespace Temporal {
    * without a year. For example, it could be used to represent a yearly
    * recurring event, like "Bastille Day is on the 14th of July."
    *
-   * See https://tc39.es/proposal-temporal/docs/plainmonthday.html for more details.
+   * See https://tc39.es/proposal-temporal/docs/monthday.html for more details.
    */
-  export class PlainMonthDay {
+  class PlainMonthDay {
     static from(
       item: Temporal.PlainMonthDay | PlainMonthDayLike | string,
       options?: AssignmentOptions
@@ -824,20 +863,20 @@ export namespace Temporal {
     equals(other: Temporal.PlainMonthDay | PlainMonthDayLike | string): boolean;
     with(monthDayLike: PlainMonthDayLike, options?: AssignmentOptions): Temporal.PlainMonthDay;
     toPlainDate(year: { year: number }): Temporal.PlainDate;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: ShowCalendarOption): string;
     valueOf(): never;
     readonly [Symbol.toStringTag]: 'Temporal.PlainMonthDay';
   }
 
-  export type PlainTimeLike = {
-    hour?: number;
-    minute?: number;
-    second?: number;
-    millisecond?: number;
-    microsecond?: number;
-    nanosecond?: number;
+  type PlainTimeLike = {
+    hour?: number | undefined;
+    minute?: number | undefined;
+    second?: number | undefined;
+    millisecond?: number | undefined;
+    microsecond?: number | undefined;
+    nanosecond?: number | undefined;
   };
 
   /**
@@ -853,9 +892,9 @@ export namespace Temporal {
    * `Temporal.PlainDateTime` by combining it with a `Temporal.PlainDate` using the
    * `toPlainDateTime()` method.
    *
-   * See https://tc39.es/proposal-temporal/docs/plaintime.html for more details.
+   * See https://tc39.es/proposal-temporal/docs/time.html for more details.
    */
-  export class PlainTime {
+  class PlainTime {
     static from(item: Temporal.PlainTime | PlainTimeLike | string, options?: AssignmentOptions): Temporal.PlainTime;
     static compare(
       one: Temporal.PlainTime | PlainTimeLike | string,
@@ -890,7 +929,7 @@ export namespace Temporal {
     round(
       roundTo: RoundTo<'hour' | 'minute' | 'second' | 'millisecond' | 'microsecond' | 'nanosecond'>
     ): Temporal.PlainTime;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: ToStringPrecisionOptions): string;
     valueOf(): never;
@@ -898,22 +937,17 @@ export namespace Temporal {
   }
 
   /**
-   * To provide a time zone to any non-constructor Temporal method, any of the
-   * following are allowed:
-   * - An IANA time zone ID string like "Europe/Paris"
-   * - An RFC 9557 string that includes a time zone annotation like
-   *   "2025-03-13T05:40:57.499+01:00[Europe/Paris]"
-   * - A `Temporal.ZonedDateTime` object
-   */
-  export type TimeZoneLike = string | ZonedDateTime;
+   * Any of these types can be passed to Temporal methods instead of a time zone ID.
+   * */
+  type TimeZoneLike = string | ZonedDateTime;
 
-  export type PlainYearMonthLike = {
+  type PlainYearMonthLike = {
     era?: string | undefined;
     eraYear?: number | undefined;
-    year?: number;
-    month?: number;
-    monthCode?: string;
-    calendar?: CalendarLike;
+    year?: number | undefined;
+    month?: number | undefined;
+    monthCode?: string | undefined;
+    calendar?: CalendarLike | undefined;
   };
 
   /**
@@ -921,9 +955,9 @@ export namespace Temporal {
    * example, it could be used to represent a particular instance of a monthly
    * recurring event, like "the June 2019 meeting".
    *
-   * See https://tc39.es/proposal-temporal/docs/plainyearmonth.html for more details.
+   * See https://tc39.es/proposal-temporal/docs/yearmonth.html for more details.
    */
-  export class PlainYearMonth {
+  class PlainYearMonth {
     static from(
       item: Temporal.PlainYearMonth | PlainYearMonthLike | string,
       options?: AssignmentOptions
@@ -959,32 +993,32 @@ export namespace Temporal {
       options?: DifferenceOptions<'year' | 'month'>
     ): Temporal.Duration;
     toPlainDate(day: { day: number }): Temporal.PlainDate;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: ShowCalendarOption): string;
     valueOf(): never;
     readonly [Symbol.toStringTag]: 'Temporal.PlainYearMonth';
   }
 
-  export type ZonedDateTimeLike = {
+  type ZonedDateTimeLike = {
     era?: string | undefined;
     eraYear?: number | undefined;
-    year?: number;
-    month?: number;
-    monthCode?: string;
-    day?: number;
-    hour?: number;
-    minute?: number;
-    second?: number;
-    millisecond?: number;
-    microsecond?: number;
-    nanosecond?: number;
-    offset?: string;
-    timeZone?: TimeZoneLike;
-    calendar?: CalendarLike;
+    year?: number | undefined;
+    month?: number | undefined;
+    monthCode?: string | undefined;
+    day?: number | undefined;
+    hour?: number | undefined;
+    minute?: number | undefined;
+    second?: number | undefined;
+    millisecond?: number | undefined;
+    microsecond?: number | undefined;
+    nanosecond?: number | undefined;
+    offset?: string | undefined;
+    timeZone?: TimeZoneLike | undefined;
+    calendar?: CalendarLike | undefined;
   };
 
-  export class ZonedDateTime {
+  class ZonedDateTime {
     static from(
       item: Temporal.ZonedDateTime | ZonedDateTimeLike | string,
       options?: ZonedDateTimeAssignmentOptions
@@ -1053,7 +1087,7 @@ export namespace Temporal {
     toPlainDateTime(): Temporal.PlainDateTime;
     toPlainDate(): Temporal.PlainDate;
     toPlainTime(): Temporal.PlainTime;
-    toLocaleString(locales?: LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
+    toLocaleString(locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string;
     toJSON(): string;
     toString(options?: ZonedDateTimeToStringOptions): string;
     valueOf(): never;
@@ -1066,7 +1100,7 @@ export namespace Temporal {
    *
    * See https://tc39.es/proposal-temporal/docs/now.html for more details.
    */
-  export const Now: {
+  const Now: {
     /**
      * Get the exact system date and time as a `Temporal.Instant`.
      *
@@ -1142,18 +1176,17 @@ export namespace Temporal {
   };
 }
 
-declare namespace Intl {
+export namespace Intl {
   type Formattable =
     | Date
     | Temporal.Instant
-    | Temporal.ZonedDateTime
     | Temporal.PlainDate
     | Temporal.PlainTime
     | Temporal.PlainDateTime
     | Temporal.PlainYearMonth
     | Temporal.PlainMonthDay;
 
-  export interface DateTimeFormat extends globalThis.Intl.DateTimeFormat {
+  interface DateTimeFormat extends globalThis.Intl.DateTimeFormat {
     /**
      * Format a date into a string according to the locale and formatting
      * options of this `Intl.DateTimeFormat` object.
@@ -1193,23 +1226,21 @@ declare namespace Intl {
     formatRangeToParts(startDate: Date | number, endDate: Date | number): globalThis.Intl.DateTimeRangeFormatPart[];
   }
 
-  export const DateTimeFormat: {
+  const DateTimeFormat: {
     /**
      * Creates `Intl.DateTimeFormat` objects that enable language-sensitive
      * date and time formatting.
      */
-    new (locales?: string | string[], options?: globalThis.Intl.DateTimeFormatOptions): DateTimeFormat;
-    (locales?: string | string[], options?: globalThis.Intl.DateTimeFormatOptions): DateTimeFormat;
+    new (locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): DateTimeFormat;
+    (locales?: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): DateTimeFormat;
 
     /**
      * Get an array containing those of the provided locales that are supported
      * in date and time formatting without having to fall back to the runtime's
      * default locale.
      */
-    supportedLocalesOf(locales: string | string[], options?: globalThis.Intl.DateTimeFormatOptions): string[];
+    supportedLocalesOf(locales: globalThis.Intl.LocalesArgument, options?: globalThis.Intl.DateTimeFormatOptions): string[];
   };
 }
 
-export { Intl as Intl };
-
 export function toTemporalInstant(this: Date): Temporal.Instant;
diff --git a/website/src/components/Playground/monaco-init.ts b/website/src/components/Playground/monaco-init.ts
index 9211c479ffbc..ed17f7463520 100644
--- a/website/src/components/Playground/monaco-init.ts
+++ b/website/src/components/Playground/monaco-init.ts
@@ -335,8 +335,8 @@ if (
         'file:///node_modules/@number-flow/react/index.d.ts',
       );
       monaco.languages.typescript.typescriptDefaults.addExtraLib(
-        `declare module "@js-temporal/polyfill" { ${temporal} }`,
-        'file:///node_modules/@js-temporal/polyfill/index.d.ts',
+        `declare module "temporal-polyfill" { ${temporal} }`,
+        'file:///node_modules/temporal-polyfill/index.d.ts',
       );
       monaco.languages.typescript.typescriptDefaults.addExtraLib(
         `declare module "uuid" { ${uuid} }`,
@@ -353,7 +353,7 @@ if (
         `declare globals { export { default as NumberFlow } from '@number-flow/react'; }`,
       );
       monaco.languages.typescript.typescriptDefaults.addExtraLib(
-        `declare globals { export { Temporal, DateTimeFormat } from '@js-temporal/polyfill'; }`,
+        `declare globals { export { Temporal, DateTimeFormat } from 'temporal-polyfill'; }`,
       );
 
       rhLibs.forEach((lib, i) => {
diff --git a/website/src/components/Playground/temporal.ts b/website/src/components/Playground/temporal.ts
new file mode 100644
index 000000000000..f9b059586ff9
--- /dev/null
+++ b/website/src/components/Playground/temporal.ts
@@ -0,0 +1,11 @@
+import { Temporal as PolyTemporal, Intl as PolyIntl } from 'temporal-polyfill';
+
+export const Temporal = globalThis.Temporal ?? PolyTemporal;
+
+export const Intl =
+  globalThis.Temporal ? globalThis.Intl : { ...globalThis.Intl, ...PolyIntl };
+
+export const DateTimeFormat =
+  globalThis.Temporal ?
+    globalThis.Intl.DateTimeFormat
+  : PolyIntl.DateTimeFormat;
diff --git a/yarn.lock b/yarn.lock
index cd16f9ef4f03..edcd9e49e6f0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3243,12 +3243,12 @@ __metadata:
     "@babel/runtime": "npm:^7.20.0"
     "@data-client/core": "workspace:*"
     "@data-client/normalizr": "workspace:*"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@types/jest": "npm:30.0.0"
     "@types/node": "npm:^24.0.0"
     immutable: "npm:5.1.5"
     nock: "npm:13.3.1"
     rollup-plugins: "workspace:*"
+    temporal-polyfill: "npm:^0.3.0"
   languageName: unknown
   linkType: soft
 
@@ -3300,11 +3300,11 @@ __metadata:
     "@anansi/browserslist-config": "npm:^1.4.2"
     "@babel/runtime": "npm:^7.20.0"
     "@data-client/endpoint": "workspace:*"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@types/jest": "npm:30.0.0"
     "@types/node": "npm:^24.0.0"
     immutable: "npm:5.1.5"
     rollup-plugins: "workspace:*"
+    temporal-polyfill: "npm:^0.3.0"
   languageName: unknown
   linkType: soft
 
@@ -3319,7 +3319,6 @@ __metadata:
     "@data-client/test": "workspace:*"
     "@data-client/use-enhanced-reducer": "workspace:^"
     "@jest/globals": "npm:^30.0.0"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@react-navigation/native": "npm:^7.0.0"
     "@react-navigation/native-stack": "npm:^7.2.0"
     "@testing-library/dom": "npm:^10.4.0"
@@ -3340,6 +3339,7 @@ __metadata:
     react-native-screens: "npm:^4.1.0"
     react-test-renderer: "npm:^19.0.0"
     rollup-plugins: "workspace:*"
+    temporal-polyfill: "npm:^0.3.0"
   peerDependencies:
     "@react-navigation/native": ^6.0.0 || ^7.0.0
     "@types/react": ^16.14.0 || ^17.0.0 || ^18.0.0 || ^19.0.0-0 || ^19.0.0
@@ -3450,7 +3450,6 @@ __metadata:
     "@data-client/core": "workspace:^"
     "@data-client/rest": "workspace:*"
     "@jest/globals": "npm:^30.0.0"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@types/jest": "npm:30.0.0"
     "@types/node": "npm:^24.0.0"
     "@vue/test-utils": "npm:^2.4.0"
@@ -3458,6 +3457,7 @@ __metadata:
     jest-mock: "npm:^30.0.0"
     nock: "npm:13.3.1"
     rollup-plugins: "workspace:*"
+    temporal-polyfill: "npm:^0.3.0"
     vue: "npm:^3.4.0"
   peerDependencies:
     "@types/vue": ^3.0.0
@@ -5296,15 +5296,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@js-temporal/polyfill@npm:^0.5.0":
-  version: 0.5.1
-  resolution: "@js-temporal/polyfill@npm:0.5.1"
-  dependencies:
-    jsbi: "npm:^4.3.0"
-  checksum: 10c0/d9a843e22167e6c98946dc03f8a480d062ece5d01ca850930c8f00af1bd99cfe513a98c3420b24a9920c47e7a61a82e5c8866da47ecdc0e7ee2cd3bf6e440b46
-  languageName: node
-  linkType: hard
-
 "@kwsites/file-exists@npm:^1.1.1":
   version: 1.1.1
   resolution: "@kwsites/file-exists@npm:1.1.1"
@@ -18718,13 +18709,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"jsbi@npm:^4.3.0":
-  version: 4.3.0
-  resolution: "jsbi@npm:4.3.0"
-  checksum: 10c0/1817ac1b50ea3f4438bcd84cadc9aee7a8657829f65b55ea6f151f401dbbd3babedbfdd3e4f481bd7b5472abb7823efa640fd7e5eee7c30cea6431f7a8b74696
-  languageName: node
-  linkType: hard
-
 "jsbn@npm:1.1.0":
   version: 1.1.0
   resolution: "jsbn@npm:1.1.0"
@@ -24663,7 +24647,6 @@ __metadata:
     "@docusaurus/preset-classic": "npm:^3.0.1"
     "@docusaurus/theme-live-codeblock": "npm:^3.0.1"
     "@docusaurus/theme-mermaid": "npm:^3.0.1"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@mdx-js/react": "npm:^3.1.0"
     "@monaco-editor/react": "npm:^4.8.0-rc.0"
     "@number-flow/react": "npm:^0.6.0"
@@ -24683,6 +24666,7 @@ __metadata:
     react-json-tree: "npm:0.20.0"
     react-live: "npm:^4.0.0"
     serve: "npm:14.2.6"
+    temporal-polyfill: "npm:^0.3.0"
     typescript: "npm:6.0.2"
     uuid: "npm:^13.0.0"
     webpack: "npm:^5.76.0"
@@ -26041,7 +26025,6 @@ __metadata:
     "@data-client/react": "workspace:*"
     "@data-client/rest": "workspace:*"
     "@data-client/test": "workspace:*"
-    "@js-temporal/polyfill": "npm:^0.5.0"
     "@react-navigation/native": "npm:^7.0.0"
     "@react-navigation/native-stack": "npm:^7.0.0"
     "@testing-library/dom": "npm:^10.4.0"
@@ -26075,6 +26058,7 @@ __metadata:
     react-test-renderer: "npm:19.2.3"
     rimraf: "npm:^6.0.0"
     rollup: "npm:4.59.0"
+    temporal-polyfill: "npm:^0.3.0"
     typescript: "npm:6.0.2"
     whatwg-fetch: "npm:3.0.0"
   languageName: unknown
@@ -27921,6 +27905,22 @@ __metadata:
   languageName: node
   linkType: hard
 
+"temporal-polyfill@npm:^0.3.0":
+  version: 0.3.2
+  resolution: "temporal-polyfill@npm:0.3.2"
+  dependencies:
+    temporal-spec: "npm:0.3.1"
+  checksum: 10c0/762795c94e1b6cb0574541d0b09f805ff23b0a2c9d0356ab3fc0205e390a3bce73e047de2fdc54c7d149d6e6d781aa1d95aa62afa5de4c83cb79c129b0e502da
+  languageName: node
+  linkType: hard
+
+"temporal-spec@npm:0.3.1":
+  version: 0.3.1
+  resolution: "temporal-spec@npm:0.3.1"
+  checksum: 10c0/e38eae391bd59ae675f1925a65c8ef302933cf9ce98efedaf2e69269e8c36f2b5d486cd3084367f04a6c1ea0289b925690c0df20a73f0c4629b531775924e850
+  languageName: node
+  linkType: hard
+
 "term-size@npm:^2.1.0":
   version: 2.2.1
   resolution: "term-size@npm:2.2.1"