gistfile1.rb

require 'relapse'
require "active_support/all"

def parse(string)
  time = string[0].to_i.weeks.ago
  hour = string[-4, 2].to_i
  hour += 12 if string[-2, 2] == 'pm'
  time.change(hour: hour)
end

Relapse.add_time_format '3 weeks ago at 10pm', -> str { parse(str) }

Relapse.parse("3 weeks ago at 10pm") #=> 2012-10-08 22:00:00 +0100