diff --git a/modules/ui/fields/date.js b/modules/ui/fields/date.js
index 560713dd04..d410350fbb 100644
--- a/modules/ui/fields/date.js
+++ b/modules/ui/fields/date.js
@@ -22,7 +22,7 @@ export function uiFieldDate(field, context) {
 
     let edtfKey = field.key + ':edtf';
 
-    let dateTimeFormat = new Intl.DateTimeFormat(localizer.languageCode(), {
+    let dateTimeFormat = new Intl.DateTimeFormat(localizer.localeCodes(), {
         year: 'numeric',
         era: 'short',
         month: 'long',
@@ -37,7 +37,7 @@ export function uiFieldDate(field, context) {
      * @param year A representative year within the era.
      */
     function getEraName(year, format) {
-        let longFormat = new Intl.DateTimeFormat(localizer.languageCode(), {
+        let longFormat = new Intl.DateTimeFormat(localizer.localeCodes(), {
             year: 'numeric',
             era: format,
             timeZone: 'UTC',
@@ -76,7 +76,7 @@ export function uiFieldDate(field, context) {
 
     /// Returns the localized name of a month in the given format.
     function getMonthName(month, format) {
-        let longFormat = new Intl.DateTimeFormat(localizer.languageCode(), {
+        let longFormat = new Intl.DateTimeFormat(localizer.localeCodes(), {
             month: format,
             timeZone: 'UTC',
         });
diff --git a/modules/validations/invalid_format.js b/modules/validations/invalid_format.js
index eaf7c292b4..d567ded123 100644
--- a/modules/validations/invalid_format.js
+++ b/modules/validations/invalid_format.js
@@ -41,7 +41,7 @@ export function validationFormatting() {
 
                     let alternatives = [];
                     if (normalized !== null) {
-                        let label = normalized.date.toLocaleDateString(localizer.languageCode(), normalized.localeOptions);
+                        let label = normalized.date.toLocaleDateString(localizer.localeCodes(), normalized.localeOptions);
                         alternatives.push({
                             date: normalized.value,
                             label: label || normalized.value,
@@ -51,7 +51,7 @@ export function validationFormatting() {
                     if (edtfFromOSM) {
                         let label;
                         try {
-                            label = edtf.default(edtfFromOSM).format(localizer.languageCode());
+                            label = edtf.default(edtfFromOSM).format(localizer.localeCode());
                         } catch (e) {
                             label = edtfFromOSM;
                         }
@@ -105,7 +105,7 @@ export function validationFormatting() {
             if (parserError.offset && parserError.token) {
                 message = t.append('issues.invalid_format.edtf.reference', {
                     token: parserError.token.value,
-                    position: (parserError.offset + 1).toLocaleString(localizer.languageCode()),
+                    position: (parserError.offset + 1).toLocaleString(localizer.localeCodes()),
                 });
             } else if (parserError.message) {
                 message = selection => selection.append('span')