I'm sure historians must have these concepts defined. I just had a quick look at wikipedia, and it defines contemporary history as:

1) (broad) that part of history still in living memory, which they approximate as about 80 years.

2) (narrow) that part of history remembered by most adults living, which they characterise as about one generation or about 30 years.

This seems in line with several of the suggestions above and has a reasonable feel as a definition.


Mick