diff --git a/src/Controller/Administrative/SeasonAssignment/TaskDeadlineController.php b/src/Controller/Administrative/SeasonAssignment/TaskDeadlineController.php
index 7142a6e..d3c31db 100644
--- a/src/Controller/Administrative/SeasonAssignment/TaskDeadlineController.php
+++ b/src/Controller/Administrative/SeasonAssignment/TaskDeadlineController.php
@@ -46,6 +46,9 @@ class TaskDeadlineController extends AbstractController
         $form->handleRequest($request);
 
         if ($form->isSubmitted() && $form->isValid()) {
+            $applyToAll = true === $form->get('applyToAll')->getData();
+            $appliedCount = $applyToAll ? ($seasonAssignment?->applyDeadlinesToOpenTasks($task) ?? 0) : 0;
+
             $this->entityManager->flush();
 
             $this->logger->info('Change season assignment task deadlines', [
@@ -54,9 +57,13 @@ class TaskDeadlineController extends AbstractController
                 'task' => $task->getTaskKey(),
                 'deadline_override_1' => $task->getDeadlineOverride1()?->format('Y-m-d'),
                 'deadline_override_2' => $task->getDeadlineOverride2()?->format('Y-m-d'),
+                'apply_to_all' => $applyToAll,
+                'applied_count' => $appliedCount,
             ]);
 
-            $this->addFlash('success', 'Die Fristen wurden gespeichert');
+            $this->addFlash('success', $applyToAll
+                ? 'Die Fristen wurden für alle offenen Einträge gespeichert'
+                : 'Die Fristen wurden gespeichert');
 
             return new HxRedirectResponse($returnUrl);
         }
diff --git a/src/Entity/SeasonAssignment.php b/src/Entity/SeasonAssignment.php
index 97d9b41..29976b1 100644
--- a/src/Entity/SeasonAssignment.php
+++ b/src/Entity/SeasonAssignment.php
@@ -208,6 +208,30 @@ class SeasonAssignment implements BlameableEntityInterface, TimestampableEntityI
         return $this;
     }
 
+    /**
+     * Copies both deadline overrides of $source onto every other entry that is not ticked off,
+     * empty ones included - an empty override resets the entry to its computed deadline. Entries
+     * already done keep theirs: their deadline is history by then.
+     *
+     * @return int the number of entries changed, $source not counted
+     */
+    public function applyDeadlinesToOpenTasks(SeasonAssignmentTask $source): int
+    {
+        $count = 0;
+
+        foreach ($this->tasks as $task) {
+            if ($task === $source || $task->isDone()) {
+                continue;
+            }
+
+            $task->setDeadlineOverride1($source->getDeadlineOverride1());
+            $task->setDeadlineOverride2($source->getDeadlineOverride2());
+            ++$count;
+        }
+
+        return $count;
+    }
+
     /**
      * @return Collection<int, Upload>
      */
diff --git a/src/Form/SeasonTaskDeadlineType.php b/src/Form/SeasonTaskDeadlineType.php
index 58e6a6b..deff894 100644
--- a/src/Form/SeasonTaskDeadlineType.php
+++ b/src/Form/SeasonTaskDeadlineType.php
@@ -4,6 +4,7 @@ namespace App\Form;
 
 use App\Entity\SeasonAssignmentTask;
 use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\CheckboxType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
@@ -27,6 +28,13 @@ class SeasonTaskDeadlineType extends AbstractType
                 'required' => false,
                 'help' => 'Ohne Angabe gilt Frist 1.',
             ])
+            // unmapped: the controller copies the entered deadlines onto the other entries
+            ->add('applyToAll', CheckboxType::class, [
+                'label' => 'auf alle Fristen anwenden',
+                'required' => false,
+                'mapped' => false,
+                'help' => 'Gilt für alle noch nicht erledigten Einträge. Leere Felder setzen deren Fristen auf den berechneten Wert zurück.',
+            ])
         ;
     }
 
diff --git a/templates/administrative/season_assignment/modal_task_deadline.html.twig b/templates/administrative/season_assignment/modal_task_deadline.html.twig
index 31c2739..4a15abc 100644
--- a/templates/administrative/season_assignment/modal_task_deadline.html.twig
+++ b/templates/administrative/season_assignment/modal_task_deadline.html.twig
@@ -10,6 +10,7 @@
         </p>
         {{ form_row(form.deadlineOverride1) }}
         {{ form_row(form.deadlineOverride2) }}
+        {{ form_row(form.applyToAll) }}
     </div>
     <button type="submit" class="btn">
         Speichern
diff --git a/tests/Entity/SeasonAssignmentTest.php b/tests/Entity/SeasonAssignmentTest.php
index 313d373..11d3fd3 100644
--- a/tests/Entity/SeasonAssignmentTest.php
+++ b/tests/Entity/SeasonAssignmentTest.php
@@ -6,6 +6,7 @@ namespace App\Tests\Entity;
 
 use App\Entity\JobProfile;
 use App\Entity\SeasonAssignment;
+use App\Entity\SeasonAssignmentTask;
 use App\Entity\Teamer;
 use PHPUnit\Framework\TestCase;
 
@@ -100,4 +101,43 @@ class SeasonAssignmentTest extends TestCase
         $this->assertSame('2027-04-30', $seasonAssignment->getDateTo()->format('Y-m-d'));
         $this->assertSame('AGR', $seasonAssignment->getHotelCode());
     }
+
+    public function testApplyingDeadlinesCopiesBothOverridesOntoOpenEntriesOnly(): void
+    {
+        $seasonAssignment = new SeasonAssignment();
+        $source = (new SeasonAssignmentTask())
+            ->setDeadlineOverride1(new \DateTimeImmutable('2026-11-15'))
+            ->setDeadlineOverride2(new \DateTimeImmutable('2026-11-30'));
+        $open = new SeasonAssignmentTask();
+        $done = (new SeasonAssignmentTask())
+            ->setDone(true)
+            ->setDeadlineOverride1(new \DateTimeImmutable('2026-10-01'));
+        $seasonAssignment->addTask($source)->addTask($open)->addTask($done);
+
+        $this->assertSame(1, $seasonAssignment->applyDeadlinesToOpenTasks($source));
+
+        $this->assertSame('2026-11-15', $open->getDeadlineOverride1()?->format('Y-m-d'));
+        $this->assertSame('2026-11-30', $open->getDeadlineOverride2()?->format('Y-m-d'));
+        $this->assertSame('2026-10-01', $done->getDeadlineOverride1()?->format('Y-m-d'));
+        $this->assertNull($done->getDeadlineOverride2());
+    }
+
+    /**
+     * Empty fields are applied as well: that is how the office resets every entry to its
+     * computed deadline in one go.
+     */
+    public function testApplyingEmptyDeadlinesResetsTheOverrides(): void
+    {
+        $seasonAssignment = new SeasonAssignment();
+        $source = new SeasonAssignmentTask();
+        $other = (new SeasonAssignmentTask())
+            ->setDeadlineOverride1(new \DateTimeImmutable('2026-11-15'))
+            ->setDeadlineOverride2(new \DateTimeImmutable('2026-11-30'));
+        $seasonAssignment->addTask($source)->addTask($other);
+
+        $seasonAssignment->applyDeadlinesToOpenTasks($source);
+
+        $this->assertNull($other->getDeadlineOverride1());
+        $this->assertNull($other->getDeadlineOverride2());
+    }
 }