I have been using my time machine to back up into an external HD regularly - like every day. I also have been using this to save a lot of my stuff including some documentaries that I watch into the HD. I would copy the video file into my MBP and then back up using time machine. Once it shows up in my backup, I delete the file from my MBP. In this way, I am freeing up space in my MBP but storing all the files so that I can retrieve and watch them later if I want to. However, I sometimes find that some files that I backup like this don't show up in my time machine. I have read that the time machine stores weekly backups and hourly backups. Let's say that I make a backup on Monday. On Tuesday I save a file, back it up and then delete the file. I back up on all the days of the week until next monday. So what exactly does a "weekly" back up mean. After a year/week/month - which backups can I expect to see in my timemachine?