Datetime changes

app.py

@@ -60,7 +60,7 @@ def log_submission(filename: str, num_chunks: int, start_time: float, status: st
     file_size_mb = round(file_size / (1024 * 1024), 2)
 
     log_entry = {
-        "timestamp": datetime.utcnow().isoformat(),
+        "timestamp": datetime.now(datetime.UTC).isoformat(),
         "filename_hash": anonymized_name,
         "file_size_mb": file_size_mb,
         "num_chunks": num_chunks,