diff --git a/specification/storage/Microsoft.BlobStorage/client.tsp b/specification/storage/Microsoft.BlobStorage/client.tsp
index 9aacc8719f89..dda836e75795 100644
--- a/specification/storage/Microsoft.BlobStorage/client.tsp
+++ b/specification/storage/Microsoft.BlobStorage/client.tsp
@@ -40,8 +40,6 @@ namespace Customizations;
   "rust"
 );
 
-@@alternateType(AccessPolicy.expiry, string, "rust");
-@@alternateType(AccessPolicy.start, string, "rust");
 @@alternateType(BlobPropertiesInternal.contentLength, uint64, "rust");
 @@alternateType(BlobContentLengthRequired.blobContentLength, uint64, "rust");
 @@alternateType(ContentLengthResponseHeader.contentLength, uint64, "rust");
diff --git a/specification/storage/Microsoft.BlobStorage/models.tsp b/specification/storage/Microsoft.BlobStorage/models.tsp
index 42e8c95799e1..d8bb4a71d55f 100644
--- a/specification/storage/Microsoft.BlobStorage/models.tsp
+++ b/specification/storage/Microsoft.BlobStorage/models.tsp
@@ -788,12 +788,12 @@ enum LeaseStatus {
 model AccessPolicy {
   /** The date-time the policy is active. */
   @Xml.name("Start")
-  @encode("rfc7231")
+  @encode("rfc3339-fixed-width")
   start: utcDateTime;
 
   /** The date-time the policy expires. */
   @Xml.name("Expiry")
-  @encode("rfc7231")
+  @encode("rfc3339-fixed-width")
   expiry: utcDateTime;
 
   /** The permissions for acl the policy. */