From 85174e1df0f29aaba61325f731c4f6f7afc429df Mon Sep 17 00:00:00 2001
From: Jonathan <523261+jcfrei@users.noreply.github.com>
Date: Wed, 29 Jul 2026 15:47:38 +0200
Subject: [PATCH] fix(ui): date locale configurable, default browser (was
 hardcoded en-US)

formatDate forced "en-US" (US month/day order + English month), so every
deployment showed US-style dates regardless of the viewer. Now numeric and
day/month per a configurable locale, defaulting to the viewer's browser locale;
setDateLocale(locale) pins it (e.g. "de-CH" -> DD.MM.YYYY). Both exported.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 CHANGELOG.md               | 13 +++++++++++++
 frontend/package-lock.json |  4 ++--
 frontend/package.json      |  2 +-
 frontend/src/index.ts      |  4 ++++
 frontend/src/lib/utils.ts  | 19 +++++++++++++++----
 pyproject.toml             |  2 +-
 6 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d86821..aeed6c1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,19 @@ semver-governed public surface — a breaking change to a seam is a major bump.
 
 ## [Unreleased]
 
+## [0.6.9] - 2026-07-29
+
+### Fixed
+- **Dates no longer force US format.** `formatDate` hardcoded the `"en-US"`
+  locale (and an English short month), so every deployment showed US-style
+  dates regardless of the viewer. It now formats numeric, day/month per the
+  configured locale, defaulting to the **viewer's browser locale**. A
+  deployment can pin it with the new **`setDateLocale(locale)`** (e.g.
+  `setDateLocale("de-CH")` for `DD.MM.YYYY` everywhere). `setDateLocale` and
+  `formatDate` are exported from the package.
+  Note: native `<input type="date">` pickers still render in the browser/OS
+  locale — that's the platform, not this formatter.
+
 ## [0.6.8] - 2026-07-29
 
 ### Added
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index 665c0c2..7bec71d 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@lambda-development/erp-core",
-  "version": "0.6.8",
+  "version": "0.6.9",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@lambda-development/erp-core",
-      "version": "0.6.8",
+      "version": "0.6.9",
       "license": "Apache-2.0",
       "dependencies": {
         "@fontsource/inter": "^5.2.8"
diff --git a/frontend/package.json b/frontend/package.json
index e9927e1..ba43523 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@lambda-development/erp-core",
-  "version": "0.6.8",
+  "version": "0.6.9",
   "description": "Frontend core of Lambda ERP — app shell, document/master pages, chat UI, reports, and extension registries.",
   "license": "Apache-2.0",
   "repository": {
diff --git a/frontend/src/index.ts b/frontend/src/index.ts
index 59fabce..2f1831a 100644
--- a/frontend/src/index.ts
+++ b/frontend/src/index.ts
@@ -55,6 +55,10 @@ export type { ListContext } from "./lib/doc-list-context";
 export { configureBranding, getBranding } from "./lib/branding";
 export type { Branding } from "./lib/branding";
 
+// Date display locale (default: viewer's browser locale). Pin per deployment,
+// e.g. setDateLocale("de-CH").
+export { setDateLocale, formatDate } from "./lib/utils";
+
 // API client
 export { api, request, ApiError, configureApiBase } from "./api/client";
 
diff --git a/frontend/src/lib/utils.ts b/frontend/src/lib/utils.ts
index c6c8f1c..1d3f3d9 100644
--- a/frontend/src/lib/utils.ts
+++ b/frontend/src/lib/utils.ts
@@ -20,13 +20,24 @@ export function formatNumber(value: number | null | undefined, decimals = 2) {
   }).format(value ?? 0);
 }
 
-/** Format a date string for display. */
+// Display locale for dates. Default: the viewer's browser locale — the old
+// hardcoded "en-US" forced US month/day order (and English month names) on
+// every deployment. A deployment can pin it, e.g. setDateLocale("de-CH") for
+// DD.MM.YYYY everywhere, regardless of the viewer's browser.
+let dateLocale: string | undefined;
+
+/** Pin the locale used by formatDate (undefined = the viewer's browser locale). */
+export function setDateLocale(locale: string | undefined) {
+  dateLocale = locale;
+}
+
+/** Format a date string for display (numeric, day-first per the locale). */
 export function formatDate(value: string | null | undefined) {
   if (!value) return "";
-  return new Date(value).toLocaleDateString("en-US", {
+  return new Date(value).toLocaleDateString(dateLocale, {
     year: "numeric",
-    month: "short",
-    day: "numeric",
+    month: "2-digit",
+    day: "2-digit",
   });
 }
 
diff --git a/pyproject.toml b/pyproject.toml
index 62a6bd5..ab8e43d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "lambda-erp"
-version = "0.6.8"
+version = "0.6.9"
 description = "Core ERP logic - accounting, sales, purchasing, inventory"
 readme = "README.md"
 license = "Apache-2.0"