I wrote a Flickr Time Machine application, its pretty basic, just searches on a year, and returns the pictures on flickr that have been tagged with that year, you can only go back in time of course, it would be cool if you could go forwards but not possible hehe ;-)
Of course it could do with some refinements, such as search by date photo was taken or date range searching and date and tag searching, i might try and improve the code one day when i get some time.