Nickel is a client for Natural Inputs
sudo gem install lzell-nickel
Then try it out:
require 'rubygems'
require 'nickel'
n = Nickel.query "party this friday at 10pm"
n.message # => party
n.occurrences.first.start_date # => 20090403
n.occurrences.first.start_time # => 22:00:00
Many more examples here.