diff --git a/src/relative-time.ts b/src/relative-time.ts
index 39b02cf..bbc1c82 100644
--- a/src/relative-time.ts
+++ b/src/relative-time.ts
@@ -168,7 +168,7 @@ export default class RelativeTime {
   }
 
   formatDate(): string {
-    let format = isDayFirst() ? '%e %b' : '%b %e'
+    let format = isDayFirst(this.locale) ? '%e %b' : '%b %e'
     if (!isThisYear(this.date)) {
       format += isYearSeparator() ? ', %Y' : ' %Y'
     }
diff --git a/src/utils.ts b/src/utils.ts
index 5fa8345..14e7b80 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -91,14 +91,13 @@ export function strftime(time: Date, formatString: string): string {
   })
 }
 
-export function makeFormatter(options: Intl.DateTimeFormatOptions): () => Intl.DateTimeFormat | undefined {
-  let format: Intl.DateTimeFormat | null
-  return function (): Intl.DateTimeFormat | undefined {
-    if (format) return format
+export function makeFormatter(
+  options: Intl.DateTimeFormatOptions
+): (locale?: string) => Intl.DateTimeFormat | undefined {
+  return function (locale?: string): Intl.DateTimeFormat | undefined {
     if ('Intl' in window) {
       try {
-        format = new Intl.DateTimeFormat(undefined, options)
-        return format
+        return new Intl.DateTimeFormat(locale, options)
       } catch (e) {
         if (!(e instanceof RangeError)) {
           throw e
@@ -108,7 +107,7 @@ export function makeFormatter(options: Intl.DateTimeFormatOptions): () => Intl.D
   }
 }
 
-let dayFirst: boolean | null = null
+let dayFirst: Record<string, boolean> = {}
 const dayFirstFormatter = makeFormatter({day: 'numeric', month: 'short'})
 
 // Private: Determine if the day should be formatted before the month name in
@@ -116,16 +115,16 @@ const dayFirstFormatter = makeFormatter({day: 'numeric', month: 'short'})
 // for en-US.
 //
 // Returns true if the day appears before the month.
-export function isDayFirst(): boolean {
-  if (dayFirst !== null) {
-    return dayFirst
+export function isDayFirst(locale: string = 'default'): boolean {
+  if (locale in dayFirst) {
+    return dayFirst[locale]
   }
 
-  const formatter = dayFirstFormatter()
+  const formatter = dayFirstFormatter(locale)
   if (formatter) {
     const output = formatter.format(new Date(0))
-    dayFirst = !!output.match(/^\d/)
-    return dayFirst
+    dayFirst[locale] = !!output.match(/^\d/)
+    return dayFirst[locale]
   } else {
     return false
   }
diff --git a/test/relative-time.js b/test/relative-time.js
index be31a35..1b504c0 100644
--- a/test/relative-time.js
+++ b/test/relative-time.js
@@ -114,6 +114,7 @@ suite('relative-time', function () {
   test('switches to dates after 30 past days', function () {
     const now = new Date(Date.now() - 30 * 60 * 60 * 24 * 1000).toISOString()
     const time = document.createElement('relative-time')
+    time.setAttribute('lang', 'en-US')
     time.setAttribute('datetime', now)
     assert.match(time.textContent, /on [A-Z][a-z]{2} \d{1,2}/)
   })
@@ -121,6 +122,7 @@ suite('relative-time', function () {
   test('switches to dates after 30 future days', function () {
     const now = new Date(Date.now() + 30 * 60 * 60 * 24 * 1000).toISOString()
     const time = document.createElement('relative-time')
+    time.setAttribute('lang', 'en-US')
     time.setAttribute('datetime', now)
     assert.match(time.textContent, /on [A-Z][a-z]{2} \d{1,2}/)
   })