I backup to an external drive and up until now, the backups were at the very top of that drive's finder window, and in the expected format: "2011-11-17 2042" for date and time. I just did a backup of this weekend's work and I now have 2 backup files, one from the 17th and one from today. I've searched all my drives including the trash and those files are not to be found. But at least I know they are not being overwritten.