diff --git a/web/src/app/journal/[slug]/opengraph-image.test.tsx b/web/src/app/journal/[slug]/opengraph-image.test.tsx
new file mode 100644
index 000000000..77320f761
--- /dev/null
+++ b/web/src/app/journal/[slug]/opengraph-image.test.tsx
@@ -0,0 +1,57 @@
+// The card a post shows when its link is shared printed the frontmatter date
+// as it is written: "2026-05-14T01:30:00+09:00" across the top right of all
+// 37 cards, on 27 October.
+
+import { isValidElement, type ReactElement, type ReactNode } from "react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { getAllJournalPosts } from "@/lib/journal";
+import OpenGraphImage from "./opengraph-image";
+
+vi.mock("next/og", () => ({
+  ImageResponse: class {
+    element: ReactElement;
+    constructor(element: ReactElement) {
+      this.element = element;
+    }
+  },
+}));
+
+function strings(node: ReactNode): string[] {
+  if (typeof node === "string" || typeof node === "number") return [String(node)];
+  if (Array.isArray(node)) return node.flatMap(strings);
+  if (isValidElement(node)) return strings((node.props as { children?: ReactNode }).children);
+  return [];
+}
+
+async function cardText(slug: string) {
+  const card = (await OpenGraphImage({ params: Promise.resolve({ slug }) })) as unknown as {
+    element: ReactElement;
+  };
+  return strings(card.element);
+}
+
+afterEach(() => {
+  vi.unstubAllEnvs();
+});
+
+describe("journal share card", () => {
+  it("prints the day the post was written in Seoul, not the frontmatter string", async () => {
+    vi.stubEnv("TZ", "UTC");
+    const text = await cardText("headache");
+
+    expect(text).toContain("May 14, 2026");
+    expect(text).not.toContain("2026-05-14T01:30:00+09:00");
+  });
+
+  it("gives no card a raw timestamp", async () => {
+    vi.stubEnv("TZ", "UTC");
+    const raw: string[] = [];
+
+    for (const post of getAllJournalPosts({ includeDrafts: true })) {
+      const text = await cardText(post.slug);
+      if (text.some((line) => /\d{4}-\d{2}-\d{2}T/.test(line))) raw.push(post.slug);
+    }
+
+    expect(raw).toEqual([]);
+  });
+});
diff --git a/web/src/app/journal/[slug]/opengraph-image.tsx b/web/src/app/journal/[slug]/opengraph-image.tsx
index dcf8299d3..40c38e3a0 100644
--- a/web/src/app/journal/[slug]/opengraph-image.tsx
+++ b/web/src/app/journal/[slug]/opengraph-image.tsx
@@ -1,5 +1,5 @@
 import { ImageResponse } from "next/og";
-import { getAllJournalPosts, getJournalSlugs } from "@/lib/journal";
+import { formatJournalDate, getAllJournalPosts, getJournalSlugs } from "@/lib/journal";
 
 export const runtime = "nodejs";
 export const size = {
@@ -51,7 +51,9 @@ export default async function OpenGraphImage({ params }: OpenGraphImageProps) {
           }}
         >
           <span>patternflow / journal</span>
-          <span>{post?.date ?? ""}</span>
+          {/* The Korean and the English page share this card, and its top
+              line is English capitals, so the date is the English one. */}
+          <span>{post ? formatJournalDate(post.date, "en") : ""}</span>
         </div>
         <div
           style={{