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I hope this question doesn't get too broad, I'm having a hard time formulating the problem clearly.

Let's say you have a set of JPEG pictures. All of the files' date attributes are set to a recent date (and created == modified for any given file). To illustrate:

FILENAME    CREATED            MODIFIED
file1.jpg   2013-07-20 15:30   2013-07-20 15:30
file2.jpg   2013-07-20 15:37   2013-07-20 15:37
file3.jpg   2013-07-20 16:00   2013-07-20:16:00

Someone tells you this is inaccurate, because the dates were overwritten during multiple backup/copy operations, possibly involving CD burning and a migration from a Windows file-system to Mac. That the photos are in fact much older. However, the time span of the attributes seems pretty natural (15:30, 15:37...) and corresponds with the images' content well, while "overwritten" times would surely span a shorter period (15:30, 15:30, 15:30; 15:31...)

  • Is the natural time span any proof the dates are actual creation dates?
  • What operations could, always will, and won't ever affect these attributes?
  • Can you think of a way to disprove them, or the other way, confirm they're telling the truth? Or is it a "we'll never know" situation?

Additional notes:

I always assumed the following about these attributes:

  • Date created is the day the file was written to camera's memory card; when I copy it to my hard drive, it doesn't get modified
  • Date modified is the date of last modification of file's content; original value same as date created; gets overwritten everytime I hit Save in some graphics editor; DOES NOT get overwritten when I copy the file

If I'm wrong, please correct me. However even if I'm right, the situation can get a bit more complicated:

I randomly checked some of my old photos (which also lived through some backups / copying), and the dates don't make sense - sometimes date created is more recent than date modified. They were both the same when I took the picture, and I imagine date modified stayed the same since I never opened the file in any editor, and date created was somehow changed during some backup process. So in this case, the date modified attribute is the actual creation date.

The point is, only date attribute I trust is stored in EXIF metadata. But I can't view them, because I don't have access to the photos. And even if I could, could I trust the EXIF date 100% (provided the camera's date was set correctly) or can even this information get accidentally overwritten by some operation (other that on purpose with some EXIF editor) ?

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Date Created on Windows at least seems to be be based on when the file first existed on the current drive/volume. So if you copied a photo from a memory card to your hard drive then the Date Created field would have been set at that point. Date modified should not be set unless the content of the file has actually been changed somehow. I would say that the Date Taken field in the EXIF should be the most reliable field. If the date is wrong on the camera then the Date Created and Date Modified fields in the memory card's file system are also going to be wrong. –  James Nov 24 '13 at 17:00

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