diff --git a/app/views/entries/_form.html.erb b/app/views/entries/_form.html.erb
index 7134cb1..d5c1d1b 100644
--- a/app/views/entries/_form.html.erb
+++ b/app/views/entries/_form.html.erb
@@ -223,6 +223,26 @@
             clearFields(); // alle Quellen löschen
         }
 
+        function calculateEndTimeFromStart() {
+            if (!startInput.value || baseTotalMinutes === 0) return;
+
+            const [sh, sm] = startInput.value.split(":").map(Number);
+            const startDate = new Date(2000, 0, 1, sh, sm);
+
+            let minutesToAdd = baseTotalMinutes;
+            if (breakCheckbox && breakCheckbox.checked) minutesToAdd = Math.max(0, baseTotalMinutes - 30);
+
+            const endDate = new Date(startDate.getTime() + minutesToAdd * 60000);
+            const hh = String(endDate.getHours()).padStart(2, '0');
+            const mm = String(endDate.getMinutes()).padStart(2, '0');
+
+            endInput.value = `${hh}:${mm}`;
+        }
+
+        startInput.addEventListener("change", function () {
+            calculateEndTimeFromStart();
+        });
+
         // Listeners
         if (startInput && endInput) {
             startInput.addEventListener("change", calculateFromTimes);