diff --git a/app.py b/app.py
index 7b023bd..1d0c600 100644
--- a/app.py
+++ b/app.py
@@ -1267,17 +1267,38 @@ def favicon():
 @app.route("/")
 def main_page():
     now = datetime.now(timezone.utc)
-    month_str = request.args.get("month") or now.strftime("%Y-%m")
+
+    month_param = request.args.get("month", None)  # surowy parametr z URL
     start = end = None
 
-    if month_str:
+    if month_param in (None, ""):
+        # brak wyboru -> domyślnie aktualny miesiąc
+        month_str = now.strftime("%Y-%m")
+        start = datetime(now.year, now.month, 1, tzinfo=timezone.utc)
+        end = (start + timedelta(days=31)).replace(day=1)
+
+    elif month_param == "all":
+        month_str = "all"
+        start = end = None
+
+    else:
+        month_str = month_param
         try:
             year, month = map(int, month_str.split("-"))
             start = datetime(year, month, 1, tzinfo=timezone.utc)
             end = (start + timedelta(days=31)).replace(day=1)
-        except:
+        except ValueError:
             start = end = None
 
+    # dalej normalnie używasz date_filter:
+    def date_filter(query):
+        if start and end:
+            query = query.filter(
+                ShoppingList.created_at >= start,
+                ShoppingList.created_at < end
+            )
+        return query
+
     def date_filter(query):
         if start and end:
             query = query.filter(
diff --git a/templates/main.html b/templates/main.html
index 12193a4..b1dc50c 100644
--- a/templates/main.html
+++ b/templates/main.html
@@ -47,7 +47,9 @@
         {{ month_names[month|int - 1] }} {{ year }}
       </option>
     {% endfor %}
-    <option value="">Wyświetl wszystko</option>
+    <option value="all" {% if selected_month == 'all' %}selected{% endif %}>
+      Wyświetl wszystko
+    </option>
   </select>
 </div>
 
@@ -235,7 +237,8 @@
               {{ month_names[month|int - 1] }} {{ year }}
             </a>
           {% endfor %}
-          <a href="{{ url_for('main_page') }}" class="btn btn-outline-secondary {% if not selected_month %}active{% endif %}">
+          <a href="{{ url_for('main_page', month='all') }}"
+            class="btn btn-outline-secondary {% if selected_month == 'all' %}active{% endif %}">
             📋 Wyświetl wszystkie
           </a>
         </div>