fix(timestamps): localize events and reject malformed ledger dates

frontend/src/__tests__/events.test.ts

@@ -25,6 +25,26 @@ import {
 } from "@/services/events";
 
 describe("ledgerClosedAtToUnixSeconds", () => {
+  const expected = Date.UTC(2026, 1, 26, 15, 4) / 1000;
+
+  it.each([
+    ["ISO string", "2026-02-26T15:04:00.000Z"],
+    ["numeric milliseconds", Date.UTC(2026, 1, 26, 15, 4)],
+    ["Date", new Date("2026-02-26T15:04:00.000Z")],
+  ])("accepts a valid %s", (_label, value) => {
+    expect(ledgerClosedAtToUnixSeconds(value)).toBe(expected);
+  });
+
+  it.each([
+    ["invalid string", "not-a-date"],
+    ["missing value", undefined],
+    ["NaN", Number.NaN],
+    ["positive infinity", Number.POSITIVE_INFINITY],
+    ["negative infinity", Number.NEGATIVE_INFINITY],
+  ])("throws RangeError for %s", (_label, value) => {
+    expect(() =>
+      ledgerClosedAtToUnixSeconds(value as unknown as string)
+    ).toThrow(new RangeError("Invalid ledger close timestamp"));
   const expectedSeconds = Date.UTC(2026, 6, 18, 8, 30) / 1000;
 
   it.each([
@@ -53,6 +73,16 @@ describe("ledgerClosedAtToUnixSeconds", () => {
 });
 
 describe("pollMarketEvents", () => {
+  it("discards an event with malformed ledgerClosedAt", async () => {
+    const malformedEvent = {
+      topic: ["market_cancelled", 7],
+      value: {},
+      ledgerClosedAt: "not-a-date",
+      txHash: "malformed-event",
+    };
+
+    mocks.getLatestLedger.mockResolvedValue({ sequence: 100 });
+    mocks.getEvents.mockResolvedValue({ events: [malformedEvent] });
   it("drops an event with a malformed close timestamp", async () => {
     mocks.getLatestLedger.mockResolvedValue({ sequence: 100 });
     mocks.getEvents.mockResolvedValue({

frontend/src/__tests__/helpers.test.ts

@@ -35,6 +35,8 @@ import {
   formatXLM,
   truncateAddress,
   isValidAmount,
+  formatDate,
+  formatTime,
   timeUntil,
   formatDate,
   formatTime,
@@ -46,6 +48,22 @@ import {
   timeAgo,
 } from "@/utils/helpers";
 
+describe("localized timestamp formatters", () => {
+  const timestamp = Date.UTC(2026, 2, 1, 1, 30) / 1000;
+
+  it.each([
+    ["en-US", "UTC", "Mar 1, 2026, 01:30 AM", "01:30 AM"],
+    ["en-US", "America/New_York", "Feb 28, 2026, 08:30 PM", "08:30 PM"],
+    ["en-US", "Asia/Ho_Chi_Minh", "Mar 1, 2026, 08:30 AM", "08:30 AM"],
+    ["vi-VN", "UTC", "01:30 1 thg 3, 2026", "01:30"],
+    ["vi-VN", "America/New_York", "20:30 28 thg 2, 2026", "20:30"],
+    ["vi-VN", "Asia/Ho_Chi_Minh", "08:30 1 thg 3, 2026", "08:30"],
+  ])("formats %s in %s independently of the test machine", (locale, timeZone, date, time) => {
+    expect(formatDate(timestamp, locale, timeZone)).toBe(date);
+    expect(formatTime(timestamp, locale, timeZone)).toBe(time);
+  });
+});
+
 // ── formatXLM ─────────────────────────────────────────────────────────────────
 
 describe("formatXLM", () => {

frontend/src/app/markets/[id]/page.tsx

@@ -7,6 +7,7 @@ import { useWallet } from "@/hooks/useWallet";
 import { useToken } from "@/hooks/useToken";
 import { pollMarketEvents } from "@/services/events";
 import { getXlmBalance } from "@/services/soroban";
+import { displayXLM, formatTime, formatXLM, calculatePayout, truncateAddress } from "@/utils/helpers";
 import {
   WIN_POINTS,
   LOSE_POINTS,

frontend/src/services/events.ts

@@ -19,6 +19,20 @@ function isKnownEventType(s: string): s is ContractEventType {
   return (EVENT_TYPES as readonly string[]).includes(s);
 }
 
+/** Convert the ledger close time to the app's Unix-seconds timestamp contract. */
+export function ledgerClosedAtToUnixSeconds(
+  ledgerClosedAt: string | number | Date
+): number {
+  const timestampMs =
+    ledgerClosedAt instanceof Date
+      ? ledgerClosedAt.getTime()
+      : new Date(ledgerClosedAt).getTime();
+
+  if (!Number.isFinite(timestampMs)) {
+    throw new RangeError("Invalid ledger close timestamp");
+  }
+
+  return Math.floor(timestampMs / 1000);
 const MILLISECOND_TIMESTAMP_THRESHOLD = 100_000_000_000;
 const ISO_TIMESTAMP_WITH_TIME_ZONE =
   /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(?:\.\d{1,9})?(?:[zZ]|[+-](\d{2}):(\d{2}))$/;

frontend/src/types/index.ts

@@ -129,6 +129,7 @@ export interface MarketEvent {
   user: string;
   marketId: number;
   amount?: number;
+  /** Unix timestamp in seconds. */
   timestamp: number;
   txHash: string;
 }

frontend/src/utils/helpers.ts

@@ -53,6 +53,41 @@ export function timeUntil(timestamp: number): string {
   return `${diff}s`;
 }
 
+const DATE_TIME_OPTIONS: Intl.DateTimeFormatOptions = {
+  year: "numeric",
+  month: "short",
+  day: "numeric",
+  hour: "2-digit",
+  minute: "2-digit",
+};
+
+const TIME_OPTIONS: Intl.DateTimeFormatOptions = {
+  hour: "2-digit",
+  minute: "2-digit",
+};
+
+/** Format Unix seconds in the viewer's locale and time zone by default. */
+export function formatDate(
+  timestamp: number,
+  locale?: string | string[],
+  timeZone?: string
+): string {
+  return new Intl.DateTimeFormat(locale, {
+    ...DATE_TIME_OPTIONS,
+    ...(timeZone ? { timeZone } : {}),
+  }).format(new Date(timestamp * 1000));
+}
+
+/** Format Unix seconds as a localized time of day. */
+export function formatTime(
+  timestamp: number,
+  locale?: string | string[],
+  timeZone?: string
+): string {
+  return new Intl.DateTimeFormat(locale, {
+    ...TIME_OPTIONS,
+    ...(timeZone ? { timeZone } : {}),
+  }).format(new Date(timestamp * 1000));
 /**
  * Format a Unix timestamp (seconds) to a locale-aware date/time string.
  *