Deleting of Log Files and Backup Files

I just wanted to follow up on a couple of post that I found in here. Both of the post where about long Running Backups. If my understanding is correct, SQL Backup looks at all of the files in the Log directory or the backup Directory to make sure that it is a SQL Backup file before it deletes it. Does it look at all of the files regardless of Creation/Modified data/time or only the files that meet the deletion time frame.