Dave Hoover picked up the ball from my "next-weekday" post and submitted a contribution to the Ruby Facets project. Now Ruby Facets lets you require 'facets/more/times' and say things like 1.weekday.ago, 4.weekdays.from_now, and 9.weekdays.since(some_time).
Have a look at the source. Thanks for your work preparing this contribution, Dave!