diff --git a/sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/rest_client.hpp b/sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/rest_client.hpp
index cb6f59c01d..9300ba96e4 100644
--- a/sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/rest_client.hpp
+++ b/sdk/storage/azure-storage-files-shares/inc/azure/storage/files/shares/rest_client.hpp
@@ -2034,7 +2034,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
         std::string FileAttributes;
         Nullable<std::string> FileCreationTime;
         Nullable<std::string> FileLastWriteTime;
-        Nullable<DateTime> FileChangeTime;
+        Nullable<std::string> FileChangeTime;
       };
       static Response<Models::CreateDirectoryResult> Create(
           Core::Http::_internal::HttpPipeline& pipeline,
@@ -2065,7 +2065,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
         std::string FileAttributes;
         Nullable<std::string> FileCreationTime;
         Nullable<std::string> FileLastWriteTime;
-        Nullable<DateTime> FileChangeTime;
+        Nullable<std::string> FileChangeTime;
       };
       static Response<Models::SetDirectoryPropertiesResult> SetProperties(
           Core::Http::_internal::HttpPipeline& pipeline,
@@ -2158,7 +2158,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
         std::string FileAttributes;
         Nullable<std::string> FileCreationTime;
         Nullable<std::string> FileLastWriteTime;
-        Nullable<DateTime> FileChangeTime;
+        Nullable<std::string> FileChangeTime;
         Nullable<std::string> LeaseId;
       };
       static Response<Models::CreateFileResult> Create(
@@ -2210,7 +2210,7 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
         std::string FileAttributes;
         Nullable<std::string> FileCreationTime;
         Nullable<std::string> FileLastWriteTime;
-        Nullable<DateTime> FileChangeTime;
+        Nullable<std::string> FileChangeTime;
         Nullable<std::string> LeaseId;
       };
       static Response<Models::SetFilePropertiesResult> SetHttpHeaders(
diff --git a/sdk/storage/azure-storage-files-shares/src/rest_client.cpp b/sdk/storage/azure-storage-files-shares/src/rest_client.cpp
index 6967141004..2c46a7bbcc 100644
--- a/sdk/storage/azure-storage-files-shares/src/rest_client.cpp
+++ b/sdk/storage/azure-storage-files-shares/src/rest_client.cpp
@@ -3,7 +3,8 @@
 // Licensed under the MIT License.
 //
 // Code generated by Microsoft (R) AutoRest C++ Code Generator.
-// Changes may cause incorrect behavior and will be lost if the code is regenerated.
+// Changes may cause incorrect behavior and will be lost if the code is
+// regenerated.
 #include <azure/storage/files/shares/rest_client.hpp>
 
 #include <algorithm>
@@ -187,8 +188,8 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
     const CopyStatus CopyStatus::Success("success");
     const CopyStatus CopyStatus::Aborted("aborted");
     const CopyStatus CopyStatus::Failed("failed");
-    const FileLastWrittenMode FileLastWrittenMode::Now("Now");
-    const FileLastWrittenMode FileLastWrittenMode::Preserve("Preserve");
+    const FileLastWrittenMode FileLastWrittenMode::Now("now");
+    const FileLastWrittenMode FileLastWrittenMode::Preserve("preserve");
     const PermissionCopyMode PermissionCopyMode::Source("source");
     const PermissionCopyMode PermissionCopyMode::Override("override");
   } // namespace Models
@@ -1691,11 +1692,9 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       {
         request.SetHeader("x-ms-file-last-write-time", options.FileLastWriteTime.Value());
       }
-      if (options.FileChangeTime.HasValue())
+      if (options.FileChangeTime.HasValue() && !options.FileChangeTime.Value().empty())
       {
-        request.SetHeader(
-            "x-ms-file-change-time",
-            options.FileChangeTime.Value().ToString(Azure::DateTime::DateFormat::Rfc1123));
+        request.SetHeader("x-ms-file-change-time", options.FileChangeTime.Value());
       }
       auto pRawResponse = pipeline.Send(request, context);
       auto httpStatusCode = pRawResponse->GetStatusCode();
@@ -1848,11 +1847,9 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       {
         request.SetHeader("x-ms-file-last-write-time", options.FileLastWriteTime.Value());
       }
-      if (options.FileChangeTime.HasValue())
+      if (options.FileChangeTime.HasValue() && !options.FileChangeTime.Value().empty())
       {
-        request.SetHeader(
-            "x-ms-file-change-time",
-            options.FileChangeTime.Value().ToString(Azure::DateTime::DateFormat::Rfc1123));
+        request.SetHeader("x-ms-file-change-time", options.FileChangeTime.Value());
       }
       auto pRawResponse = pipeline.Send(request, context);
       auto httpStatusCode = pRawResponse->GetStatusCode();
@@ -2645,11 +2642,9 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       {
         request.SetHeader("x-ms-file-last-write-time", options.FileLastWriteTime.Value());
       }
-      if (options.FileChangeTime.HasValue())
+      if (options.FileChangeTime.HasValue() && !options.FileChangeTime.Value().empty())
       {
-        request.SetHeader(
-            "x-ms-file-change-time",
-            options.FileChangeTime.Value().ToString(Azure::DateTime::DateFormat::Rfc1123));
+        request.SetHeader("x-ms-file-change-time", options.FileChangeTime.Value());
       }
       if (options.LeaseId.HasValue() && !options.LeaseId.Value().empty())
       {
@@ -3080,11 +3075,9 @@ namespace Azure { namespace Storage { namespace Files { namespace Shares {
       {
         request.SetHeader("x-ms-file-last-write-time", options.FileLastWriteTime.Value());
       }
-      if (options.FileChangeTime.HasValue())
+      if (options.FileChangeTime.HasValue() && !options.FileChangeTime.Value().empty())
       {
-        request.SetHeader(
-            "x-ms-file-change-time",
-            options.FileChangeTime.Value().ToString(Azure::DateTime::DateFormat::Rfc1123));
+        request.SetHeader("x-ms-file-change-time", options.FileChangeTime.Value());
       }
       if (options.LeaseId.HasValue() && !options.LeaseId.Value().empty())
       {
diff --git a/sdk/storage/azure-storage-files-shares/swagger/README.md b/sdk/storage/azure-storage-files-shares/swagger/README.md
index cb9b88e431..08c73e7b9b 100644
--- a/sdk/storage/azure-storage-files-shares/swagger/README.md
+++ b/sdk/storage/azure-storage-files-shares/swagger/README.md
@@ -219,6 +219,8 @@ directive:
       $.ShareEnabledProtocols["enum"] = ["Smb", "Nfs"];
       $.ShareEnabledProtocols["x-ms-enum"] = {"name": "ShareProtocols", "modelAsString": false};
       $.ShareEnabledProtocols["x-ms-enum"]["values"] = [{"value": "SMB", "name": "Smb"},{"value": "NFS", "name": "Nfs"}];
+      delete $.FileChangeTime.format;
+      $.FileLastWriteTimeMode["x-ms-enum"]["values"] = [{"value": "now", "name": "Now"},{"value": "preserve", "name": "Preserve"}];
   - from: swagger-document
     where: $.definitions
     transform: >