snow leopardtime-machine
I use a 2 TB drive for Time Machine and have used the disk for about a year or two.
Today I wanted to check on an old file (an old version of MonoDevelop) and found out that my oldest backup is from January this year.
I checked the disk itself and found that it really only contains folders for dates starting in January.
What did Time Machine do to my old backups???
(There was always enough room on the disk and there are 1.4 TB free now. I never deleted anything in the backups.backupdb folder.)
Enter TimeMachine, then in the main window, select the backup you want to delete (on the right), then use the Action Menu (Gear icon) to select "Delete Backup".
Using this menu, you can also, when a file or a folder is selected, delete all its backup.
By default, Time Machine keeps the following backups:
If there's space constraints then Time Machine will start to delete the backups, but otherwise it keeps them for as long as possible.
To get to the individual photos you will have to have iPhoto as the active window when you activate Time Machine from the menu bar. This lets you go back and see all of the photos. If you did it from the Finder it's more complex because iPhoto bundles its whole library into one big package.
Best Answer
The system will delete old backups if it has an estimate that it will need the space for the impending backup. Normally the system over estimates a backup by 2 to 4 GB in routine use, but I have seen some cases where it had estimates of 250 GB or more due to some folder changes. Even without an error in estimation, you could have attached an external drive that increased this estimate drastically.
Only you have the logs and data to know how plausible this is. Check out BackupLoupe if you like to have better measurements on how each backup differs in size from the others.
For this reason, I periodically duplicate my Time Machine drives (or choose to rotate them monthly) so that if there is a bug, I can look when I swap in the new drive to make sure I don't lose some of my older history.