diff --git a/__tests__/lib/validations.test.ts b/__tests__/lib/validations.test.ts
index b712821..5b3c117 100644
--- a/__tests__/lib/validations.test.ts
+++ b/__tests__/lib/validations.test.ts
@@ -10,7 +10,29 @@ const bikeSchema = z.object({
     .min(1, 'Name darf nicht nur aus Leerzeichen bestehen'),
   brand: z.string().optional().transform((val) => val?.trim() || undefined),
   model: z.string().optional().transform((val) => val?.trim() || undefined),
-  purchaseDate: z.string().datetime().optional().or(z.date().optional()),
+  purchaseDate: z
+    .union([z.date(), z.string()])
+    .optional()
+    .transform((val) => {
+      if (!val || val === undefined) return undefined
+      if (val instanceof Date) {
+        return isNaN(val.getTime()) ? undefined : val
+      }
+      if (typeof val === 'string') {
+        // Handle YYYY-MM-DD format (from HTML date input)
+        if (/^\d{4}-\d{2}-\d{2}$/.test(val)) {
+          const date = new Date(val + 'T00:00:00.000Z')
+          return isNaN(date.getTime()) ? undefined : date
+        }
+        // Handle ISO datetime format or any other parseable date string
+        const date = new Date(val)
+        return isNaN(date.getTime()) ? undefined : date
+      }
+      return undefined
+    })
+    .refine((val) => val === undefined || val instanceof Date, {
+      message: 'Ungültiges Datumsformat',
+    }),
   notes: z.string().optional().transform((val) => val?.trim() || undefined),
 })