How do I format a date in ruby to include "rd" as in "3rd"

I'm going to echo everyone else, but I'll just encourage you to download the activesupport gem, so you can just use it as a library. You don't need all of Rails to use ordinalize.

% gem install activesupport
...
% irb 
irb> require 'rubygems'
#=>  true
irb> require 'activesupport'
#=>  true
irb> 3.ordinalize
#=>  "3rd"

created_at.strftime("#{created_at.day.ordinalize} of %m, %y")

Will produce "4th of July, 2009"

Unless you're using Rails, add this ordinalize method (code shamelessly lifted from the Rails source) to the Fixnum class

class Fixnum
  def ordinalize
    if (11..13).include?(self % 100)
      "#{self}th"
    else
      case self % 10
        when 1; "#{self}st"
        when 2; "#{self}nd"
        when 3; "#{self}rd"
        else    "#{self}th"
      end
    end
  end
end

Then format your date like this:

> now = Time.now
> puts now.strftime("#{now.day.ordinalize} of %B, %Y")
=> 4th of July, 2009

I don't think Ruby has it, but if you have Rails, try this:-

puts 3.ordinalize #=> "3rd"