diff --git a/core/src/main/scala/org/apache/spark/ui/SparkUI.scala b/core/src/main/scala/org/apache/spark/ui/SparkUI.scala
index db1f8bc1a2ff..ac154b793856 100644
--- a/core/src/main/scala/org/apache/spark/ui/SparkUI.scala
+++ b/core/src/main/scala/org/apache/spark/ui/SparkUI.scala
@@ -167,7 +167,7 @@ private[spark] class SparkUI private (
         attemptId = None,
         startTime = new Date(startTime),
         endTime = new Date(-1),
-        duration = 0,
+        duration = System.currentTimeMillis() - startTime,
         lastUpdated = new Date(startTime),
         sparkUser = getSparkUser,
         completed = false,
diff --git a/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala b/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
index 45348b2e9a7b..79496bba6674 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISeleniumSuite.scala
@@ -700,7 +700,14 @@ class UISeleniumSuite extends SparkFunSuite with WebBrowser with Matchers {
       parseDate(attempts(0) \ "startTime") should be (sc.startTime)
       parseDate(attempts(0) \ "endTime") should be (-1)
       val oneAppJsonAst = getJson(sc.ui.get, "")
-      oneAppJsonAst should be (appListJsonAst.children(0))
+      val duration = attempts(0) \ "duration"
+      oneAppJsonAst \\ "duration" should not be duration
+      // SPARK-42697: duration will increase as the app is running
+      // Replace the duration before we compare the full JObjects
+      val durationAdjusted = oneAppJsonAst.transformField {
+        case ("duration", _) => ("duration", duration)
+      }
+      durationAdjusted should be (appListJsonAst.children(0))
     }
   }