diff --git a/specification/chaos/resource-manager/Microsoft.Chaos/preview/2022-10-01-preview/types/experiments.json b/specification/chaos/resource-manager/Microsoft.Chaos/preview/2022-10-01-preview/types/experiments.json
index 0db5ecc7df22..f279536f95ba 100644
--- a/specification/chaos/resource-manager/Microsoft.Chaos/preview/2022-10-01-preview/types/experiments.json
+++ b/specification/chaos/resource-manager/Microsoft.Chaos/preview/2022-10-01-preview/types/experiments.json
@@ -212,7 +212,8 @@
         "duration": {
           "type": "string",
           "description": "ISO8601 formatted string that represents a duration.",
-          "pattern": "^P(\\d+Y)?(\\d+M)?(\\d+D)?(T(\\d+H)?(\\d+M)?(\\d+(\\.\\d+)?S)?)?$"
+          "pattern": "^P(\\d+Y)?(\\d+M)?(\\d+D)?(T(\\d+H)?(\\d+M)?(\\d+(\\.\\d+)?S)?)?$",
+          "format": "duration"
         }
       },
       "required": [
@@ -265,7 +266,8 @@
         "duration": {
           "type": "string",
           "description": "ISO8601 formatted string that represents a duration.",
-          "pattern": "^P(\\d+Y)?(\\d+M)?(\\d+D)?(T(\\d+H)?(\\d+M)?(\\d+(\\.\\d+)?S)?)?$"
+          "pattern": "^P(\\d+Y)?(\\d+M)?(\\d+D)?(T(\\d+H)?(\\d+M)?(\\d+(\\.\\d+)?S)?)?$",
+          "format": "duration"
         },
         "parameters": {
           "description": "List of key value pairs.",