@ Burton: I think he meant the other way, at least from the example on the linked page:
Chronic.parse('tomorrow')
#=> Mon Aug 28 12:00:00 PDT 2006
Chronic.parse('monday', :context => :past)
#=> Mon Aug 21 12:00:00 PDT 2006
Chronic.parse('this tuesday 5:00')
#=> Tue Aug 29 17:00:00 PDT 2006
I thought I would take a stab at it too until I realized! (nice implementation though)