Fix for Python 3.13

#9

Author: ndejong

src/hibp_downloader/models/stats.py

@@ -168,5 +168,5 @@ def __init__(self, results: List[PrefixMetadata]):
             elif item.data_source == PrefixMetadataDataSource.unknown_source_status:
                 data["unknown_source_status_count"] += 1
 
-        data["start_time"] = (oldest_timestamp - datetime.fromtimestamp(0).astimezone()).total_seconds()
+        data["start_time"] = oldest_timestamp.timestamp()
         self.stats = QueueItemStats(**data)