(and by extension, in social software enabled content management systems, especially moblogging ones)
Currently, Flickr timestamps everything in it's developers' timezone, Pacific Standard Time. To anyone not on the western seaboard of North America, this is pretty much useless. Who bothers doing timezone conversions when looking at friend's pictures? ;)
So, two options: display the timestamp based in the timezone of the poster or, even better, in the viewer's. The former is arguably also just more metacrap, the latter is a far more useful frame of reference for the viewer.
"Ohhh he/she posted this 20 minutes ago / while I was making coffee, he/she was in a restaurant in Shibuya / etc..."
Brings you closer to me, you know. :)