diff --git a/services/dataProcessor.ts b/services/dataProcessor.ts
index c529371..246be48 100644
--- a/services/dataProcessor.ts
+++ b/services/dataProcessor.ts
@@ -195,21 +195,25 @@ const normalizeMonth = (rawMonth: string): string => {
     // 2. Handle numeric months "01", "1", "01-2023"
     // If it's a full date string like "2023-04-01", "01/04/2023", or "23/2/26" (DD/M/YY)
     if (m.includes('/') || m.includes('-')) {
-        // Handle DD/M/YY or DD/MM/YY (European day-first format, e.g. "23/2/26" = 23 Feb 2026)
-        const parts = m.split(m.includes('/') ? '/' : '-');
+        // Handle date strings with 3 parts separated by '/' or '-'
+        const sep = m.includes('/') ? '/' : '-';
+        const parts = m.split(sep);
         if (parts.length === 3) {
             const [a, b, c] = parts.map(p => parseInt(p, 10));
             if (!isNaN(a) && !isNaN(b) && !isNaN(c)) {
-                // If first part > 12: definitely day-first → DD/MM/YY
-                if (a > 12 && b >= 1 && b <= 12) {
-                    const yearShort = c < 100 ? String(c).padStart(2, '0') : String(c).slice(2);
+                // YYYY-MM-DD or YYYY/MM/DD (ISO-like, year is 4 digits in first position)
+                if (a > 31 && b >= 1 && b <= 12) {
+                    const yearShort = String(a).slice(2);
                     const result = `${MONTH_ORDER[b - 1]}-${yearShort}`;
                     monthCache[rawMonth] = result;
                     return result;
                 }
-                // YYYY/MM/DD or YYYY-MM-DD (ISO-like, year is 4 digits in first position)
-                if (a > 31 && b >= 1 && b <= 12) {
-                    const yearShort = String(a).slice(2);
+                // DD/M/YY European format (e.g. "5/1/26"=5 Jan 2026, "23/2/26"=23 Feb 2026).
+                // When last part is a 2-digit year and middle part is a valid month, always
+                // treat as day-first (Spanish/EU convention). Covers ambiguous cases like
+                // "5/1/26" where day <= 12, avoiding JS Date's US MM/DD/YY misparse.
+                if (c < 100 && b >= 1 && b <= 12 && a >= 1 && a <= 31) {
+                    const yearShort = String(c).padStart(2, '0');
                     const result = `${MONTH_ORDER[b - 1]}-${yearShort}`;
                     monthCache[rawMonth] = result;
                     return result;