Ideal fix, doesn't work

src/locale/i18n.ts

@@ -9,6 +9,7 @@ import '@formatjs/intl-pluralrules/locale-data/en'
 import '@formatjs/intl-numberformat/locale-data/en'
 
 import {useEffect} from 'react'
+import {getCalendars} from 'expo-localization'
 import {i18n} from '@lingui/core'
 
 import {sanitizeAppLanguageSetting} from '#/locale/helpers'
@@ -46,6 +47,20 @@ import {messages as messagesZh_HK} from '#/locale/locales/zh-HK/messages'
 import {messages as messagesZh_TW} from '#/locale/locales/zh-TW/messages'
 import {useLanguagePrefs} from '#/state/preferences'
 
+/**
+ * Set default time zone for Intl.DateTimeFormat polyfill from formatjs
+ * {@link https://formatjs.github.io/docs/polyfills/intl-datetimeformat/#default-timezone}
+ *
+ * According to docs, `getCalendars` is guaranteed to have at least one
+ * calendar, and for now this ONLY returns one calendar.
+ * {@link https://docs.expo.dev/versions/latest/sdk/localization/#localizationgetcalendars}
+ */
+if ('__setDefaultTimeZone' in Intl.DateTimeFormat) {
+  console.log('Setting default time zone', getCalendars()[0].timeZone)
+  // @ts-ignore
+  Intl.DateTimeFormat.__setDefaultTimeZone(getCalendars()[0].timeZone)
+}
+
 /**
  * We do a dynamic import of just the catalog that we need
  */