diff --git a/src/services/npdi.rs b/src/services/npdi.rs
index 7cb0597..478ee9e 100644
--- a/src/services/npdi.rs
+++ b/src/services/npdi.rs
@@ -1,4 +1,5 @@
 use std::io::Cursor;
+use chrono::{DateTime, NaiveDateTime, Utc};
 use rocket::http::{Header, Status};
 use rocket::{Data, State};
 use rocket::response::{Response, Responder};
@@ -14,16 +15,20 @@ pub struct DataResponder<T> {
     content_disposition_header: Header<'static>,
     content_transfer_encoding_header: Header<'static>,
     content_length_header: Header<'static>,
+    last_modified_header: Header<'static>,
 }
 
 impl<'r, 'o: 'r, T: Responder<'r, 'o>> DataResponder<T> {
-    fn new(inner: T, content_length: String) -> Self {
+    fn new(inner: T, content_length: String, updated: NaiveDateTime) -> Self {
+        let updated_utc: DateTime<Utc> = DateTime::from_naive_utc_and_offset(updated, Utc);
+
         DataResponder {
             inner,
             content_type_header: Header::new("Content-Type", "applicatoin/octet-stream"), // Intentional spelling mistake
             content_disposition_header: Header::new("Content-Disposition", "attachment"),
             content_transfer_encoding_header: Header::new("Content-Transfer-Encoding", "binary"),
             content_length_header: Header::new("Content-Length", content_length),
+            last_modified_header: Header::new("Last-Modified", updated_utc.format("%a, %d %b %Y %H:%M:%S GMT").to_string()),
         }
     }
 }
@@ -61,5 +66,5 @@ pub async fn data(pool: &State<Pool>, s3: &State<S3Client>,boss_app_id: String,
         .into_bytes()
         .to_vec();
 
-    Ok(DataResponder::new(data, file_wup.size.to_string()))
+    Ok(DataResponder::new(data, file_wup.size.to_string(), file_wup.updated))
 }
\ No newline at end of file