diff --git a/calculator/index.html b/calculator/index.html
index a5be37e..9a6b3f7 100644
--- a/calculator/index.html
+++ b/calculator/index.html
@@ -128,7 +128,14 @@
         tr.id = rowId;
         // Date cell
         const dateCell = document.createElement('td');
-        dateCell.className = 'px-1 bg-neutral-200 w-16';
+        let dateCellClass = 'px-1 w-16 ';
+        // Weekend: Saturday (6) or Sunday (0)
+        if (date.getDay() === 0 || date.getDay() === 6) {
+          dateCellClass += 'bg-neutral-500';
+        } else {
+          dateCellClass += 'bg-neutral-200';
+        }
+        dateCell.className = dateCellClass;
         dateCell.id = `date-${dateString}`;
         dateCell.innerText = label;
         tr.appendChild(dateCell);