diff --git a/nmdc_runtime/api/core/util.py b/nmdc_runtime/api/core/util.py
index 48d15ed1..ff3bcb4a 100644
--- a/nmdc_runtime/api/core/util.py
+++ b/nmdc_runtime/api/core/util.py
@@ -28,10 +28,13 @@ def hash_from_str(s: str, algo="sha256") -> str:
     return getattr(hashlib, algo)(s.encode("utf-8")).hexdigest()
 
 
-def sha256hash_from_file(file_path: str):
+def sha256hash_from_file(file_path: str, timestamp: str):
     # https://stackoverflow.com/a/55542529
     h = hashlib.sha256()
 
+    timestamp_bytes = timestamp.encode('utf-8')
+    h.update(timestamp_bytes)
+
     with open(file_path, "rb") as file:
         while True:
             # Reading is buffered, so we can read smaller chunks.
diff --git a/nmdc_runtime/api/endpoints/util.py b/nmdc_runtime/api/endpoints/util.py
index fd473682..35c63a5a 100644
--- a/nmdc_runtime/api/endpoints/util.py
+++ b/nmdc_runtime/api/endpoints/util.py
@@ -442,6 +442,7 @@ def persist_content_and_get_drs_object(
                     ),
                     "access_methods": [{"access_id": drs_id}],
                 },
+                timestamp= datetime.now(tz=ZoneInfo('America/Los_Angeles')).isoformat(timespec='minutes')
             )
         )
     self_uri = f"drs://{HOSTNAME_EXTERNAL}/{drs_id}"
diff --git a/nmdc_runtime/util.py b/nmdc_runtime/util.py
index 23e94dd1..475a98d4 100644
--- a/nmdc_runtime/util.py
+++ b/nmdc_runtime/util.py
@@ -82,7 +82,7 @@ def put_object(filepath, url, mime_type=None):
         return requests.put(url, data=f, headers={"Content-Type": mime_type})
 
 
-def drs_metadata_for(filepath, base=None):
+def drs_metadata_for(filepath, base=None, timestamp=None):
     """given file path, get drs metadata
 
     required: size, created_time, and at least one checksum.
@@ -96,7 +96,7 @@ def drs_metadata_for(filepath, base=None):
         )
     if "checksums" not in base:
         base["checksums"] = [
-            {"type": "sha256", "checksum": sha256hash_from_file(filepath)}
+            {"type": "sha256", "checksum": sha256hash_from_file(filepath, timestamp)}
         ]
     if "mime_type" not in base:
         base["mime_type"] = mimetypes.guess_type(filepath)[0]