diff --git a/CHANGES.txt b/CHANGES.txt
index dfb849d532..c4f4c1f8ef 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 3.12
+ * Add timeUnit Days for cassandra-stress (CASSANDRA-13029)
  * Add mutation size and batch metrics (CASSANDRA-12649)
  * Add method to get size of endpoints to TokenMetadata (CASSANDRA-12999)
  * Fix primary index calculation for SASI (CASSANDRA-12910)
diff --git a/tools/stress/src/org/apache/cassandra/stress/settings/SettingsCommand.java b/tools/stress/src/org/apache/cassandra/stress/settings/SettingsCommand.java
index c3a171e7a6..1416b8bb18 100644
--- a/tools/stress/src/org/apache/cassandra/stress/settings/SettingsCommand.java
+++ b/tools/stress/src/org/apache/cassandra/stress/settings/SettingsCommand.java
@@ -96,6 +96,9 @@ public abstract class SettingsCommand implements Serializable
                 case 'h':
                     this.durationUnits = TimeUnit.HOURS;
                     break;
+                case 'd':
+                    this.durationUnits = TimeUnit.DAYS;
+                    break;
                 default:
                     throw new IllegalStateException();
             }
@@ -135,7 +138,7 @@ public abstract class SettingsCommand implements Serializable
 
     static class Duration extends Options
     {
-        final OptionSimple duration = new OptionSimple("duration=", "[0-9]+[smh]", null, "Time to run in (in seconds, minutes or hours)", true);
+        final OptionSimple duration = new OptionSimple("duration=", "[0-9]+[smhd]", null, "Time to run in (in seconds, minutes, hours or days)", true);
         @Override
         public List<? extends Option> options()
         {