Fix date columns showing numbers instead of dates

src/App.tsx

@@ -162,6 +162,16 @@ export default function App() {
               }
             }
 
+            // Handle date columns - Excel serial dates are numbers >= 25569 (Jan 1, 1970)
+            if (header.includes('date') || header.includes('launch') || header.includes('ready')) {
+              if (typeof val === 'number' && val >= 25569 && val <= 60000) {
+                const excelEpoch = new Date(1899, 11, 30);
+                const date = new Date(excelEpoch.getTime() + val * 86400000);
+                return date.toLocaleDateString('en-GB', { day: '2-digit', month: '2-digit', year: 'numeric' });
+              }
+              return val;
+            }
+
             const formatKeywords = ['price', 'eur', 'cost', 'msrp', 'net', 'gross', 'netto', 'brutto', 'pp', 'pph', 'uvp', 'vpe', 'stk', 'nw', 'gw', 'weight', 'kg'];
             const shouldFormat = formatKeywords.some(kw => header.includes(kw));
 

src/components/MatrixView.tsx

@@ -21,6 +21,16 @@ export function MatrixView({ data, headers }: MatrixViewProps) {
     // Convert header to lowercase for checks
     const h = header.toLowerCase();
 
+    // Handle date columns - Excel serial dates are numbers >= 25569 (Jan 1, 1970)
+    if (h.includes('date') || h.includes('launch') || h.includes('ready')) {
+      if (typeof val === 'number' && val >= 25569 && val <= 60000) {
+        const excelEpoch = new Date(1899, 11, 30);
+        const date = new Date(excelEpoch.getTime() + val * 86400000);
+        return date.toLocaleDateString('en-GB', { day: '2-digit', month: '2-digit', year: 'numeric' });
+      }
+      return val;
+    }
+
     // Always format weight/NW/GW/kg columns to 2 decimals — checked before any exclusion logic
     if (h.includes('nw') || h.includes('gw') || h.includes('weight') || h.includes('kg')) {
       if (typeof val === 'number') return val.toFixed(2);