diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
index cc8c275e40bf..c762fda011f2 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/HttpSigningConfiguration.mustache
@@ -193,7 +193,7 @@ namespace {{packageName}}.Client
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-ConditionalSerialization/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-httpclient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net47/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient-net5.0/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
index 1d2d0019caee..4ead821d7d2d 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/HttpSigningConfiguration.cs
@@ -193,7 +193,7 @@ private enum PrivateKeyType
                 }
                 else if (header.Equals(HEADER_DATE))
                 {
-                    var utcDateTime = dateTime.ToString("r").ToString();
+                    var utcDateTime = dateTime.ToUniversalTime().ToString("r");
                     HttpSignatureHeader.Add(header.ToLower(), utcDateTime);
                     HttpSignedRequestHeader.Add(HEADER_DATE, utcDateTime);
                 }