diff --git a/openapi/openapiv2.json b/openapi/openapiv2.json
index b10dd36bb..a34f866b5 100644
--- a/openapi/openapiv2.json
+++ b/openapi/openapiv2.json
@@ -13500,6 +13500,11 @@
         "startDelay": {
           "type": "string",
           "description": "Time to wait before making the first activity task available for dispatch. This delay is not applied to retry attempts."
+        },
+        "executionTime": {
+          "type": "string",
+          "format": "date-time",
+          "description": "The time at which the first activity task is made available for dispatch, computed as\n`schedule_time + start_delay`. Same as `schedule_time` if `start_delay` is not set."
         }
       },
       "description": "Information about a standalone activity."
diff --git a/openapi/openapiv3.yaml b/openapi/openapiv3.yaml
index 15e3d9f8e..52f8dd853 100644
--- a/openapi/openapiv3.yaml
+++ b/openapi/openapiv3.yaml
@@ -9852,6 +9852,12 @@ components:
           pattern: ^-?(?:0|[1-9][0-9]{0,11})(?:\.[0-9]{1,9})?s$
           type: string
           description: Time to wait before making the first activity task available for dispatch. This delay is not applied to retry attempts.
+        executionTime:
+          type: string
+          description: |-
+            The time at which the first activity task is made available for dispatch, computed as
+             `schedule_time + start_delay`. Same as `schedule_time` if `start_delay` is not set.
+          format: date-time
       description: Information about a standalone activity.
     ActivityExecutionListInfo:
       type: object
diff --git a/temporal/api/activity/v1/message.proto b/temporal/api/activity/v1/message.proto
index 6aa787203..db134d301 100644
--- a/temporal/api/activity/v1/message.proto
+++ b/temporal/api/activity/v1/message.proto
@@ -186,6 +186,10 @@ message ActivityExecutionInfo {
 
     // Time to wait before making the first activity task available for dispatch. This delay is not applied to retry attempts.
     google.protobuf.Duration start_delay = 37;
+
+    // The time at which the first activity task is made available for dispatch, computed as
+    // `schedule_time + start_delay`. Same as `schedule_time` if `start_delay` is not set.
+    google.protobuf.Timestamp execution_time = 38;
 }
 
 // Limited activity information returned in the list response.