Like the files on my computer, the Info shows a Created On date, and a Last Modified date. If we know the Created On date, we will have a clearer picture (pun intended) of when the photo was taken.
The date the Websleuth poster named FastLikeLight found by Using Firefox. "View image", "View Image info", "General" is not the same thing you are talking about. The date the picture was last modified on his Steam profile was "Tuesday, November 13, 2012 7:43:56 PM"
**The timing of him putting it up on Steam is significant, IMO. No matter when the photo was actually "taken".