diff --git a/app/Models/Foundation/Summit/Events/SummitEvent.php b/app/Models/Foundation/Summit/Events/SummitEvent.php
index 64ca573f2..1e4ad7979 100644
--- a/app/Models/Foundation/Summit/Events/SummitEvent.php
+++ b/app/Models/Foundation/Summit/Events/SummitEvent.php
@@ -1770,6 +1770,12 @@ public function setDuration(int $duration_in_seconds, bool $skipDatesSetting = f
         if (!$this->type->isAllowsPublishingDates()) {
             throw new ValidationException("Type does not allows Publishing Period.");
         }
+        // Once an event is published, only summit admins may change its duration.
+        // The published path silently shifts end_date via _setDuration when start_date
+        // is set, which would move a live schedule slot for any non-admin caller.
+        if ($this->isPublished() && !is_null($member) && !$member->isSummitAllowed($this->getSummit())) {
+            throw new ValidationException("Cannot modify duration of a published event.");
+        }
         $this->_setDuration($this->getSummit(), $duration_in_seconds, $skipDatesSetting, $member);
     }
 
diff --git a/tests/SummitEventModelTest.php b/tests/SummitEventModelTest.php
index a337efdbe..5ca6817f1 100644
--- a/tests/SummitEventModelTest.php
+++ b/tests/SummitEventModelTest.php
@@ -11,11 +11,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  **/
+use models\main\Member;
 use models\summit\SummitEvent;
 use models\summit\Presentation;
 use LaravelDoctrine\ORM\Facades\EntityManager;
 use Doctrine\Persistence\ObjectRepository;
 use Illuminate\Support\Facades\DB;
+use models\exceptions\ValidationException;
 use DateTimeZone;
 use DateTime;
 use DateInterval;
@@ -77,4 +79,28 @@ public function testChangingEndDateShouldRecalculateDuration(){
         $new_duration = $presentation->getDuration();
         $this->assertTrue($old_duration < $new_duration);
     }
+
+    public function testNonAdminMemberCannotChangeDurationOnPublishedEvent(){
+        $presentation = self::$presentations[0];
+        $this->assertTrue($presentation->isPublished());
+
+        $member = Mockery::mock(Member::class)->makePartial();
+        $member->shouldReceive('isSummitAllowed')->andReturn(false);
+
+        $this->expectException(ValidationException::class);
+        $presentation->setDuration(864000, false, $member);
+    }
+
+    public function testAdminMemberCanChangeDurationOnPublishedEvent(){
+        $presentation = self::$presentations[0];
+        $this->assertTrue($presentation->isPublished());
+
+        $member = Mockery::mock(Member::class)->makePartial();
+        $member->shouldReceive('isSummitAllowed')->andReturn(true);
+
+        $old_end_date = $presentation->getEndDate();
+        $presentation->setDuration(864000, false, $member);
+        $new_end_date = $presentation->getEndDate();
+        $this->assertTrue($old_end_date < $new_end_date);
+    }
 }
\ No newline at end of file