From 58c229ae7e2987bdcee707c647e13912d5482b7e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 13 Nov 2025 07:04:01 +0000
Subject: [PATCH 1/7] Initial plan


From 94074d65b92ce5602d3b067f56fd514421508d6b Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 13 Nov 2025 07:10:24 +0000
Subject: [PATCH 2/7] Fix date format to use RFC 1123 format instead of
 culture-dependent format

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs | 4 ++--
 DevProxy.Plugins/Behavior/RateLimitingPlugin.cs     | 2 +-
 DevProxy.Plugins/Behavior/RetryAfterPlugin.cs       | 2 +-
 DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs | 4 ++--
 DevProxy.Plugins/Mocking/MockResponsePlugin.cs      | 2 +-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
index d7911602..1367af77 100644
--- a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
+++ b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
@@ -289,7 +289,7 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
     {
         var session = e.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
         if (errorStatus == HttpStatusCode.TooManyRequests)
@@ -330,7 +330,7 @@ private void UpdateProxyBatchResponse(ProxyRequestArgs ev, GraphBatchResponsePay
 
         var session = ev.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
 
diff --git a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
index 44864c19..b210450e 100644
--- a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
@@ -246,7 +246,7 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
             if (ProxyUtils.IsGraphRequest(request))
             {
                 var requestId = Guid.NewGuid().ToString();
-                var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+                var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
                 headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
                 body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
index 25e58efc..2a6c96b9 100644
--- a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
@@ -108,7 +108,7 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
         if (ProxyUtils.IsGraphRequest(request))
         {
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
             headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
             body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
index d3d0f717..10321d9c 100644
--- a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
@@ -62,7 +62,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         {
             GraphBatchResponsePayloadResponse? response = null;
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
             var headers = ProxyUtils
                 .BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
 
@@ -155,7 +155,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         }
 
         var batchRequestId = Guid.NewGuid().ToString();
-        var batchRequestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+        var batchRequestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var batchHeaders = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, batchRequestId, batchRequestDate);
         var batchResponse = new GraphBatchResponsePayload
         {
diff --git a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
index 69c2d1f6..269843ab 100644
--- a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
@@ -348,7 +348,7 @@ private void ProcessMockResponseInternal(ProxyRequestArgs e, MockResponse matchi
     {
         string? body = null;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString(CultureInfo.CurrentCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var headers = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
         var statusCode = HttpStatusCode.OK;
         if (matchingResponse.Response?.StatusCode is not null)

From b6301712f9513c7cfd6624beeb7fc35b88a682ec Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 13 Nov 2025 11:50:35 +0000
Subject: [PATCH 3/7] Change date format from RFC 1123 to ISO-8601 as requested

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs | 4 ++--
 DevProxy.Plugins/Behavior/RateLimitingPlugin.cs     | 2 +-
 DevProxy.Plugins/Behavior/RetryAfterPlugin.cs       | 2 +-
 DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs | 4 ++--
 DevProxy.Plugins/Mocking/MockResponsePlugin.cs      | 2 +-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
index 1367af77..de94009a 100644
--- a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
+++ b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
@@ -289,7 +289,7 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
     {
         var session = e.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
         if (errorStatus == HttpStatusCode.TooManyRequests)
@@ -330,7 +330,7 @@ private void UpdateProxyBatchResponse(ProxyRequestArgs ev, GraphBatchResponsePay
 
         var session = ev.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
 
diff --git a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
index b210450e..8e606423 100644
--- a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
@@ -246,7 +246,7 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
             if (ProxyUtils.IsGraphRequest(request))
             {
                 var requestId = Guid.NewGuid().ToString();
-                var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+                var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
                 headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
                 body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
index 2a6c96b9..1699656d 100644
--- a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
@@ -108,7 +108,7 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
         if (ProxyUtils.IsGraphRequest(request))
         {
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+            var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
             headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
             body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
index 10321d9c..0bc4b276 100644
--- a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
@@ -62,7 +62,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         {
             GraphBatchResponsePayloadResponse? response = null;
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+            var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
             var headers = ProxyUtils
                 .BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
 
@@ -155,7 +155,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         }
 
         var batchRequestId = Guid.NewGuid().ToString();
-        var batchRequestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+        var batchRequestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
         var batchHeaders = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, batchRequestId, batchRequestDate);
         var batchResponse = new GraphBatchResponsePayload
         {
diff --git a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
index 269843ab..b25337c8 100644
--- a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
@@ -348,7 +348,7 @@ private void ProcessMockResponseInternal(ProxyRequestArgs e, MockResponse matchi
     {
         string? body = null;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
         var headers = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
         var statusCode = HttpStatusCode.OK;
         if (matchingResponse.Response?.StatusCode is not null)

From 40793bbd683bc83396fcc39dc02e6ab2e7f35474 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 14 Nov 2025 11:40:45 +0000
Subject: [PATCH 4/7] Revert to RFC 1123 format as requested

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs | 4 ++--
 DevProxy.Plugins/Behavior/RateLimitingPlugin.cs     | 2 +-
 DevProxy.Plugins/Behavior/RetryAfterPlugin.cs       | 2 +-
 DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs | 4 ++--
 DevProxy.Plugins/Mocking/MockResponsePlugin.cs      | 2 +-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
index de94009a..1367af77 100644
--- a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
+++ b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
@@ -289,7 +289,7 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
     {
         var session = e.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
         if (errorStatus == HttpStatusCode.TooManyRequests)
@@ -330,7 +330,7 @@ private void UpdateProxyBatchResponse(ProxyRequestArgs ev, GraphBatchResponsePay
 
         var session = ev.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
 
diff --git a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
index 8e606423..b210450e 100644
--- a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
@@ -246,7 +246,7 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
             if (ProxyUtils.IsGraphRequest(request))
             {
                 var requestId = Guid.NewGuid().ToString();
-                var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+                var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
                 headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
                 body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
index 1699656d..2a6c96b9 100644
--- a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
@@ -108,7 +108,7 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
         if (ProxyUtils.IsGraphRequest(request))
         {
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
             headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
 
             body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
index 0bc4b276..10321d9c 100644
--- a/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/GraphMockResponsePlugin.cs
@@ -62,7 +62,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         {
             GraphBatchResponsePayloadResponse? response = null;
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
             var headers = ProxyUtils
                 .BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
 
@@ -155,7 +155,7 @@ public override async Task BeforeRequestAsync(ProxyRequestArgs e, CancellationTo
         }
 
         var batchRequestId = Guid.NewGuid().ToString();
-        var batchRequestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+        var batchRequestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var batchHeaders = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, batchRequestId, batchRequestDate);
         var batchResponse = new GraphBatchResponsePayload
         {
diff --git a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
index b25337c8..269843ab 100644
--- a/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
+++ b/DevProxy.Plugins/Mocking/MockResponsePlugin.cs
@@ -348,7 +348,7 @@ private void ProcessMockResponseInternal(ProxyRequestArgs e, MockResponse matchi
     {
         string? body = null;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("o", CultureInfo.InvariantCulture);
+        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
         var headers = ProxyUtils.BuildGraphResponseHeaders(e.Session.HttpClient.Request, requestId, requestDate);
         var statusCode = HttpStatusCode.OK;
         if (matchingResponse.Response?.StatusCode is not null)

From 550db0cde2a7d18e2e53105f7a653e7a452a950a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 14 Nov 2025 12:11:42 +0000
Subject: [PATCH 5/7] Use RFC 1123 for HTTP headers and ISO 8601 for
 InnerError.Date

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs | 8 +++++---
 DevProxy.Plugins/Behavior/RateLimitingPlugin.cs     | 8 +++++---
 DevProxy.Plugins/Behavior/RetryAfterPlugin.cs       | 8 +++++---
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
index 1367af77..5cb9632d 100644
--- a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
+++ b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
@@ -289,9 +289,11 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
     {
         var session = e.Session;
         var requestId = Guid.NewGuid().ToString();
-        var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
+        var now = DateTime.Now;
+        var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
+        var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
-        var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate);
+        var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader);
         if (errorStatus == HttpStatusCode.TooManyRequests)
         {
             var retryAfterDate = DateTime.Now.AddSeconds(Configuration.RetryAfterInSeconds);
@@ -314,7 +316,7 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
                 InnerError = new()
                 {
                     RequestId = requestId,
-                    Date = requestDate
+                    Date = requestDateInnerError
                 }
             }),
             ProxyUtils.JsonSerializerOptions
diff --git a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
index b210450e..57386e17 100644
--- a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
@@ -246,8 +246,10 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
             if (ProxyUtils.IsGraphRequest(request))
             {
                 var requestId = Guid.NewGuid().ToString();
-                var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
-                headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
+                var now = DateTime.Now;
+                var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
+                var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
+                headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader));
 
                 body = JsonSerializer.Serialize(new GraphErrorResponseBody(
                     new()
@@ -257,7 +259,7 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
                         InnerError = new()
                         {
                             RequestId = requestId,
-                            Date = requestDate
+                            Date = requestDateInnerError
                         }
                     }),
                     ProxyUtils.JsonSerializerOptions
diff --git a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
index 2a6c96b9..72792e43 100644
--- a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
@@ -108,8 +108,10 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
         if (ProxyUtils.IsGraphRequest(request))
         {
             var requestId = Guid.NewGuid().ToString();
-            var requestDate = DateTime.Now.ToString("r", CultureInfo.InvariantCulture);
-            headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDate));
+            var now = DateTime.Now;
+            var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
+            var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
+            headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader));
 
             body = JsonSerializer.Serialize(new GraphErrorResponseBody(
                 new()
@@ -119,7 +121,7 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
                     InnerError = new()
                     {
                         RequestId = requestId,
-                        Date = requestDate
+                        Date = requestDateInnerError
                     }
                 }),
                 ProxyUtils.JsonSerializerOptions

From 1bb9f12796f1db2db2186a9050780897a1a1e49d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 16 Nov 2025 11:17:22 +0000
Subject: [PATCH 6/7] Replace 'o' format with 's' format for ISO 8601 dates

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs | 2 +-
 DevProxy.Plugins/Behavior/RateLimitingPlugin.cs     | 2 +-
 DevProxy.Plugins/Behavior/RetryAfterPlugin.cs       | 2 +-
 DevProxy.Plugins/Generation/HarGeneratorPlugin.cs   | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
index 5cb9632d..fa6ddfb8 100644
--- a/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
+++ b/DevProxy.Plugins/Behavior/GraphRandomErrorPlugin.cs
@@ -291,7 +291,7 @@ private void UpdateProxyResponse(ProxyRequestArgs e, HttpStatusCode errorStatus)
         var requestId = Guid.NewGuid().ToString();
         var now = DateTime.Now;
         var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
-        var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
+        var requestDateInnerError = now.ToString("s", CultureInfo.InvariantCulture);
         var request = session.HttpClient.Request;
         var headers = ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader);
         if (errorStatus == HttpStatusCode.TooManyRequests)
diff --git a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
index 57386e17..1793008a 100644
--- a/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RateLimitingPlugin.cs
@@ -248,7 +248,7 @@ private void UpdateProxyResponse(ProxyHttpEventArgsBase e, HttpStatusCode errorS
                 var requestId = Guid.NewGuid().ToString();
                 var now = DateTime.Now;
                 var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
-                var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
+                var requestDateInnerError = now.ToString("s", CultureInfo.InvariantCulture);
                 headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader));
 
                 body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
index 72792e43..d62bcac1 100644
--- a/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
+++ b/DevProxy.Plugins/Behavior/RetryAfterPlugin.cs
@@ -110,7 +110,7 @@ private static void UpdateProxyResponse(ProxyRequestArgs e, ThrottlingInfo throt
             var requestId = Guid.NewGuid().ToString();
             var now = DateTime.Now;
             var requestDateHeader = now.ToString("r", CultureInfo.InvariantCulture);
-            var requestDateInnerError = now.ToString("o", CultureInfo.InvariantCulture);
+            var requestDateInnerError = now.ToString("s", CultureInfo.InvariantCulture);
             headers.AddRange(ProxyUtils.BuildGraphResponseHeaders(request, requestId, requestDateHeader));
 
             body = JsonSerializer.Serialize(new GraphErrorResponseBody(
diff --git a/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs b/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
index 766ef525..bcda0e41 100644
--- a/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
+++ b/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
@@ -102,7 +102,7 @@ private HarEntry CreateHarEntry(RequestLog log)
 
         var entry = new HarEntry
         {
-            StartedDateTime = currentTime.ToString("o"),
+            StartedDateTime = currentTime.ToString("s"),
             Time = 0, // We don't have actual timing data in RequestLog
             Request = new HarRequest
             {

From 8ea43c5e29f6d9cb01cba710f33d33d05183ed0d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 16 Nov 2025 12:00:11 +0000
Subject: [PATCH 7/7] Revert HarGeneratorPlugin to use 'o' format for HAR spec
 compliance

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
---
 DevProxy.Plugins/Generation/HarGeneratorPlugin.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs b/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
index bcda0e41..766ef525 100644
--- a/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
+++ b/DevProxy.Plugins/Generation/HarGeneratorPlugin.cs
@@ -102,7 +102,7 @@ private HarEntry CreateHarEntry(RequestLog log)
 
         var entry = new HarEntry
         {
-            StartedDateTime = currentTime.ToString("s"),
+            StartedDateTime = currentTime.ToString("o"),
             Time = 0, // We don't have actual timing data in RequestLog
             Request = new HarRequest
             {