Make profile SSR formatting deterministic

resources/js/lib/profileFormatters.js

@@ -0,0 +1,19 @@
+const PROFILE_LOCALE = 'en-US'
+const PROFILE_TIME_ZONE = 'UTC'
+
+export function formatProfileNumber(value) {
+  const numeric = Number(value ?? 0)
+  return Number.isFinite(numeric) ? new Intl.NumberFormat(PROFILE_LOCALE).format(numeric) : '0'
+}
+
+export function formatProfileDate(value, options = {}) {
+  if (!value) return null
+
+  const date = value instanceof Date ? value : new Date(value)
+  if (Number.isNaN(date.getTime())) return null
+
+  return new Intl.DateTimeFormat(PROFILE_LOCALE, {
+    ...options,
+    timeZone: PROFILE_TIME_ZONE,
+  }).format(date)
+}

resources/js/lib/profileFormatters.test.js

@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest'
+import { formatProfileDate, formatProfileNumber } from './profileFormatters'
+
+describe('profile formatters', () => {
+  it('uses a stable en-US number format independent of the browser locale', () => {
+    expect(formatProfileNumber(9529106)).toBe('9,529,106')
+  })
+
+  it('uses UTC for stable calendar dates at timezone boundaries', () => {
+    expect(formatProfileDate('2024-01-01T00:30:00.000Z', {
+      month: 'long',
+      day: 'numeric',
+      year: 'numeric',
+    })).toBe('January 1, 2024')
+  })
+})