About file dates and what they mean...

March 4, 2013 6:38 PM

In Windows 7 or 8 (and maybe before that) if I view the properties of a document, I get all sorts of meta information. I'm interested in the Date created element and a Content created element....

I think I understand the difference, but I would like to understand it better, so I can answer a question someone has asked me about this.

Could you please explain to me how these attributes are set, and what specific actions (if any) can cause them to change?

If a document has content created and date created elements that differ, it must be because it is a copy of the original document, right? I can think of no other way that could happen.

posted by kbanas to technology (7 answers total)

A file has three dates - Created, last modified, and last accessed.

Depending on the type of the file, it can have standard metadata with information about the file's content's last modification, how long you've had it open working on it, that sort of thing. All the MS Office formats include those "content" date/times.

And no, it doesn't really work all that intelligently... Any copies inherit that metadata (but not the actual file dates), so you could have 20 spreadsheets all saying you worked on them for weeks each - Even if you blow away everything inside them and just use the file as an empty container, that information persists.

Of course, on the flip side of this, you probably don't want to know how much info the file really has in it, even if you clear out everything you can see - Things like old versions, your undo history (in some cases), all that metadata you've just notices, etc. For anything of any importance that you sent to another person/organization, always a good policy to open an entirely new document, copy-and-paste your real work into, and save that.
posted by pla at 6:53 PM on March 4

Ok, then let's just focus on the "file creation date" of a file. Let's throw out the other cruft.

When you make a file, this date is set.

There should be no other circumstances when it is modified, yes?
posted by kbanas at 7:06 PM on March 4

Not necessarily. When you move a file from one disk volume to another, it gets copied to the new volume, and the old one is deleted. The new one gets a creation date of the time when the copy happened; it doesn't inherit the creation date from the old one.

(If you move a file within the same disk volume, however, the creation date is not changed.)
posted by Chocolate Pickle at 7:43 PM on March 4

Not necessarily. When you move a file from one disk volume to another, it gets copied to the new volume, and the old one is deleted. The new one gets a creation date of the time when the copy happened; it doesn't inherit the creation date from the old one.

(If you move a file within the same disk volume, however, the creation date is not changed.)

Huh. On my Windows 7 box, I *moved* a file out to a USB thumb drive and the file creation date stayed the same. It didn't change. When I copied it, the file create date did change.
posted by kbanas at 8:15 PM on March 4

(Maybe they fixed that.)
posted by Chocolate Pickle at 9:07 PM on March 4

There should be no other circumstances when it is modified, yes?

That's the theory.

However, Windows has filesystem API calls allowing you to set the creation, modification and/or access timestamps on any file you like to any values you like, and there are readily available tools (e.g. NirSoft BulkFileChanger, Febooti fileTweak) that use those calls, so you can't rely absolutely on file metadata reflecting reality.
posted by flabdablet at 10:13 PM on March 4 [1 favorite]

Huh. On my Windows 7 box, I *moved* a file out to a USB thumb drive and the file creation date stayed the same. It didn't change. When I copied it, the file create date did change.

That makes sense. When you move a file, you don't change anything. You just pick it up and set it somewhere else. When you copy a file, you are creating a new file that is identical to the old one. So the new copy of the file should have a creation date of today, but a content creation date of whenever the original copy was created.

Even though the mechanics of moving a file from one volume to another are copy then delete, the OS is smart enough to know that when you tell it to move, it should inherit most of the metadata of the old file.
posted by gjc at 3:39 AM on March 5