presto-hive/src/main/java/io/prestosql/plugin/hive/s3/PrestoS3FileSystem.java/PrestoS3FileSystem/lastModifiedTime
class PrestoS3FileSystem:    private static long lastModifiedTime(ObjectMetadata metadata)
    {
        Date date = metadata.getLastModified();
        return (date != null) ? date.getTime() : 0;
    }