In the real world it’s not a problem. Physical objects, like paper, clearly wears the mark of time. Paper turns yellow and get torn. Other things get scratched or changes it’s appearance in some other way that makes it obvious that it’s not new.
The digital world
There are a few pretty common ways of displaying the age of content on web pages. These are primarily date stamps, telling when something was created or last edited. There’s also different color on visited links, that in a sense also is a way of telling that content is older. At least you know that you’ve already visited the page.
But that’s about it. And often, even those cues aren’t used.
Robert Hoekman Jr. has written some about in the book, Designing the Obvious and in the article Design Stories: Sorted link-lists using “ambient signifiers” on rhjr.net. His idea is to show the age of links by displaying them in different colors. The older they are, the lighter the color.
The term to describe this is ambient signifiers. It’s not restricted to just illustrate the age of content but is the concept of giving subtle cues, to help people interpret context.
Ross Howard has written about this in the article Ambient Signifiers on Boxes and Arrows which, I think, is where the term got coined. He describes his experiences with the Tokyo subway system, where a unique chime is played on each station, giving a subtle cue for the frequent commuter of where he currently is. This gave him the idea of ambient signifiers in digital media.
Currently there are some use of ambient signifiers in the applications we use. In Firefox for example, the address bar turns yellow when you enter a secure site. On sites the current status is often visualized in some way, like if you’re logged in to a site or not.
Aurora – Mozilla Concept Browser
Adaptive Path and Mozilla Labs has developed a concept of a future browser with lot of new ways of interacting with data. It’s kind of a zooming interface where you can browse your content in a 3d view where the z-axe represents time. They visualize the age of content in two ways. First of all the farther away the content the older it is. Secondly the content fades with time. I think that is a very natural way of visualizing it and a great illustration of how ambient signifiers can be used.
Watch the concept in action in this video from Adaptive Path.