When you create a new file or duplicate an existing file, OS X uses “January 24, 1984” as a placeholder for the file’s creation date until the operation finishes and it can fill in the real creation date. January 24, 1984 is the day Apple released the original Macintosh.

To see this for yourself:

  • Open a Finder window and hit ⌘-3 to change it to the Column view
  • Find a large file or folder and hit ⌘-D to duplicate it. An iPhoto library or iTunes Media folder should do the trick
  • Once Finder starts creating the new file or folder, your selection will automatically switch to that new folder. Check the right column to see the metadata and original Macintosh release date

Thanks Kieran!