diff --git a/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java b/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
index 9d0f45e..1801159 100644
--- a/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
+++ b/stockscope/src/main/java/com/sharecomparison/presentation/WebPageController.java
@@ -21,7 +21,6 @@ public WebPageController(IPriceController priceController) {
 
     @GetMapping("/")
     public String showForm(Model model) {
-        // Defaults for empty form on first visit
         model.addAttribute("symbol1", "AAPL");
         model.addAttribute("symbol2", "MSFT");
         model.addAttribute("startDate", LocalDate.now().minusYears(1).toString());
@@ -43,6 +42,15 @@ public String compare(
         symbol1 = symbol1.trim().toUpperCase();
         symbol2 = symbol2.trim().toUpperCase();
 
+        if (start.isAfter(end)) {
+            model.addAttribute("error", "Start date must be on or before end date.");
+            model.addAttribute("symbol1", symbol1);
+            model.addAttribute("symbol2", symbol2);
+            model.addAttribute("startDate", start.toString());
+            model.addAttribute("endDate", end.toString());
+            return "index";
+        }
+
         ComparisonResult result = priceController.comparePrices(symbol1, symbol2, start, end);
 
         if (result.getSymbol1Data().isEmpty() || result.getSymbol2Data().isEmpty()) {