I agree with Matt that the divisions for history
distribution somewhat less arbitrary than 19th century vs.
20th century. I don't think it's quite the case with
literature (seems as if there are nices splits around 1770
and 1910, though).
(Samer didn't mention fine
arts, but there are fairly well-defined periods there,
as well. Since it's not that large a requirement in
most distributions, time distribution for arts seem to
get heavily skewed towards the Renaissance for visual
art and early modern for music.)
To answer
Samer's questions, however, I personally would like to
see 25-33% 20th and century content for both history
and literature.
Of course, current events
should be 100% 21st century at this point. :-P
--
eps