diff --git a/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java b/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
index 38e313c..f859a02 100644
--- a/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
+++ b/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
@@ -4,8 +4,11 @@
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
@@ -81,7 +84,26 @@ public String compare(
         if (maxPrice == minPrice) maxPrice += 1.0;
         double priceRange = maxPrice - minPrice;
 
-        int n = Math.min(data1.size(), data2.size());
+        // Align series by date: only plot dates present in both data sets
+        Map<LocalDate, PriceData> map1 = data1.stream()
+                .collect(Collectors.toMap(PriceData::getDate, p -> p, (existing, replacement) -> existing));
+        Map<LocalDate, PriceData> map2 = data2.stream()
+                .collect(Collectors.toMap(PriceData::getDate, p -> p, (existing, replacement) -> existing));
+
+        Set<LocalDate> commonDates = new LinkedHashSet<>(map1.keySet());
+        commonDates.retainAll(map2.keySet());
+        List<LocalDate> sortedDates = new ArrayList<>(commonDates);
+        sortedDates.sort(Comparator.naturalOrder());
+
+        int n = sortedDates.size();
+        if (n == 0) {
+            model.addAttribute("error", "No overlapping trading dates found for the two symbols in this range.");
+            model.addAttribute("symbol1", symbol1);
+            model.addAttribute("symbol2", symbol2);
+            model.addAttribute("startDate", start.toString());
+            model.addAttribute("endDate", end.toString());
+            return "index";
+        }
         double xStep = n > 1 ? chartWidth / (n - 1) : 0;
 
         StringBuilder path1 = new StringBuilder();
@@ -91,16 +113,17 @@ public String compare(
 
         for (int i = 0; i < n; i++) {
             double x = left + i * xStep;
+            LocalDate date = sortedDates.get(i);
 
-            PriceData p1 = data1.get(i);
+            PriceData p1 = map1.get(date);
             double y1 = bottom - ((p1.getClosingPrice() - minPrice) / priceRange) * chartHeight;
             path1.append(i == 0 ? "M" : "L").append(x).append(",").append(y1).append(" ");
-            points1.add(Map.of("x", x, "y", y1, "value", p1.getClosingPrice()));
+            points1.add(Map.of("x", x, "y", y1, "value", p1.getClosingPrice(), "date", date.toString()));
 
-            PriceData p2 = data2.get(i);
+            PriceData p2 = map2.get(date);
             double y2 = bottom - ((p2.getClosingPrice() - minPrice) / priceRange) * chartHeight;
             path2.append(i == 0 ? "M" : "L").append(x).append(",").append(y2).append(" ");
-            points2.add(Map.of("x", x, "y", y2, "value", p2.getClosingPrice()));
+            points2.add(Map.of("x", x, "y", y2, "value", p2.getClosingPrice(), "date", date.toString()));
         }
 
         Map<String, Object> chartData = new HashMap<>();