diff --git a/parakeet/src/entities/core/post.rs b/parakeet/src/entities/core/post.rs
index d7c7a9ee..f81cc985 100644
--- a/parakeet/src/entities/core/post.rs
+++ b/parakeet/src/entities/core/post.rs
@@ -617,7 +617,7 @@ impl PostEntity {
             record: serde_json::json!({
                 "$type": "app.bsky.feed.post",
                 "text": text,
-                "createdAt": created_at.to_rfc3339(),
+                "createdAt": created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
             }),
             embed: self.build_embed(&data),
             stats: RecordStats {
@@ -670,7 +670,7 @@ impl PostEntity {
                 parakeet_db::tid_util::encode_tid(data.post.rkey)
             ),
             "allow": allow,
-            "createdAt": chrono::Utc::now().to_rfc3339()
+            "createdAt": chrono::Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Millis, true)
         });
 
         Some(ThreadgateView {
diff --git a/parakeet/src/entities/core/starterpack.rs b/parakeet/src/entities/core/starterpack.rs
index 72420a9a..08811265 100644
--- a/parakeet/src/entities/core/starterpack.rs
+++ b/parakeet/src/entities/core/starterpack.rs
@@ -319,7 +319,7 @@ impl StarterpackEntity {
                 None
             },
             "feeds": Vec::<String>::new(), // TODO: Need to fix load_feed_uris to work with actor_id/rkey
-            "createdAt": indexed_at.to_rfc3339(),
+            "createdAt": indexed_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
         });
 
         // Query counts if list exists
diff --git a/parakeet/src/xrpc/app_bsky/feed/get_timeline.rs b/parakeet/src/xrpc/app_bsky/feed/get_timeline.rs
index 3bcfb2cd..6926ecda 100644
--- a/parakeet/src/xrpc/app_bsky/feed/get_timeline.rs
+++ b/parakeet/src/xrpc/app_bsky/feed/get_timeline.rs
@@ -116,7 +116,7 @@ pub async fn get_timeline(
     let cursor = if has_next && timeline_items.len() > limit as usize {
         let last_rkey = timeline_items[limit as usize - 1].0;
         let timestamp = parakeet_db::tid_util::tid_to_datetime(last_rkey);
-        Some(timestamp.to_rfc3339())
+        Some(timestamp.to_rfc3339_opts(chrono::SecondsFormat::Millis, true))
     } else {
         None
     };
@@ -263,7 +263,7 @@ pub async fn get_author_feed(
     let cursor = if has_next && posts_to_return.len() == limit as usize {
         let last_rkey = posts_to_return[posts_to_return.len() - 1].1;
         let timestamp = parakeet_db::tid_util::tid_to_datetime(last_rkey);
-        Some(timestamp.to_rfc3339())
+        Some(timestamp.to_rfc3339_opts(chrono::SecondsFormat::Millis, true))
     } else {
         None
     };
diff --git a/parakeet/src/xrpc/app_bsky/feed/likes.rs b/parakeet/src/xrpc/app_bsky/feed/likes.rs
index 193fccda..bcf83c0e 100644
--- a/parakeet/src/xrpc/app_bsky/feed/likes.rs
+++ b/parakeet/src/xrpc/app_bsky/feed/likes.rs
@@ -47,7 +47,7 @@ pub async fn get_actor_likes(
         .map(|(_, rkey)| {
             // Convert TID to timestamp for cursor
             let dt = parakeet_db::tid_util::tid_to_datetime(*rkey);
-            dt.to_rfc3339()
+            dt.to_rfc3339_opts(chrono::SecondsFormat::Millis, true)
         });
 
     // Build post URIs from results
diff --git a/parakeet/src/xrpc/app_bsky/feed/posts/queries.rs b/parakeet/src/xrpc/app_bsky/feed/posts/queries.rs
index 42119e6e..eabf132b 100644
--- a/parakeet/src/xrpc/app_bsky/feed/posts/queries.rs
+++ b/parakeet/src/xrpc/app_bsky/feed/posts/queries.rs
@@ -74,7 +74,7 @@ pub async fn get_post(
     let value = serde_json::json!({
         "$type": "app.bsky.feed.post",
         "text": post_view.record.get("text").unwrap_or(&serde_json::Value::String("".to_string())),
-        "createdAt": post_view.indexed_at.to_rfc3339(),
+        "createdAt": post_view.indexed_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
     });
 
     Ok(Json(PostRes {
diff --git a/parakeet/src/xrpc/app_bsky/graph/lists.rs b/parakeet/src/xrpc/app_bsky/graph/lists.rs
index faa7d2b6..dbcbfd9c 100644
--- a/parakeet/src/xrpc/app_bsky/graph/lists.rs
+++ b/parakeet/src/xrpc/app_bsky/graph/lists.rs
@@ -128,7 +128,7 @@ pub async fn get_list(
     // Calculate next cursor
     let cursor = item_results
         .last()
-        .map(|item| item.3.to_rfc3339());
+        .map(|item| item.3.to_rfc3339_opts(chrono::SecondsFormat::Millis, true));
 
     // Get profiles for all subject actor IDs
     let subject_ids: Vec<i32> = item_results
diff --git a/parakeet/src/xrpc/app_bsky/notification.rs b/parakeet/src/xrpc/app_bsky/notification.rs
index f191ab5f..ba7e4a41 100644
--- a/parakeet/src/xrpc/app_bsky/notification.rs
+++ b/parakeet/src/xrpc/app_bsky/notification.rs
@@ -335,8 +335,8 @@ pub async fn list_notifications(
                         .collect(),
                 ),
                 description: profile_view.description.clone(),
-                created_at: Some(profile_view.created_at.to_rfc3339()),
-                indexed_at: Some(profile_view.indexed_at.to_rfc3339()),
+                created_at: Some(profile_view.created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true)),
+                indexed_at: Some(profile_view.indexed_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true)),
             }
         } else {
             // Fallback if profile not found
@@ -386,7 +386,7 @@ pub async fn list_notifications(
             reason_subject,
             record,
             is_read,
-            indexed_at: notif.indexed_at.to_rfc3339(),
+            indexed_at: notif.indexed_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
             labels: Some(Vec::new()),
         });
     }
@@ -396,7 +396,7 @@ pub async fn list_notifications(
     let cursor = next_cursor_id.map(|id| id.to_string());
 
     // Format seen_at for response
-    let seen_at_response = seen_at.map(|dt| dt.to_rfc3339());
+    let seen_at_response = seen_at.map(|dt| dt.to_rfc3339_opts(chrono::SecondsFormat::Millis, true));
 
     tracing::info!("→ listNotifications: {:.1}ms total ({} notifications)", start.elapsed().as_secs_f64() * 1000.0, notifications.len());
 
@@ -616,7 +616,7 @@ fn build_notification_record(
                         "subject": {
                             "uri": subject_uri,
                         },
-                        "createdAt": created_at.to_rfc3339(),
+                        "createdAt": created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
                     });
                 }
             }
@@ -633,7 +633,7 @@ fn build_notification_record(
                         "subject": {
                             "uri": post_uri,
                         },
-                        "createdAt": created_at.to_rfc3339(),
+                        "createdAt": created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
                     });
                 }
             }
@@ -645,7 +645,7 @@ fn build_notification_record(
                     return serde_json::json!({
                         "$type": "app.bsky.graph.follow",
                         "subject": subject_did,
-                        "createdAt": created_at.to_rfc3339(),
+                        "createdAt": created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
                     });
                 }
             }
@@ -657,7 +657,7 @@ fn build_notification_record(
                 let mut record = serde_json::json!({
                     "$type": "app.bsky.feed.post",
                     "text": content,
-                    "createdAt": created_at.to_rfc3339(),
+                    "createdAt": created_at.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
                 });
 
                 // Construct parent/root URIs using actor_did_map