Using date ordinals in Rails through an I18n time format.

en.rb

# This goes in config/locales/en.rb (*not* en.yml)
{
  :en => {
    :date => {
      :formats => {
        :short => lambda { |date, _| "%b #{date.day.ordinalize}" },
        :long => lambda { |date, _| "%B #{date.day.ordinalize}, %Y" }
      }
    },
    :time => {
      :formats => {
        :default => lambda { |time, _| "%a, #{time.day.ordinalize} %b %Y %H:%M:%S %z" },
        :short =>  lambda { |time, _| "#{time.day.ordinalize} %b %H:%M" },
        :long =>  lambda { |time, _| "%B #{time.day.ordinalize}, %Y %H:%M" }
      }
    }
  }
}

template.html.erb

<%= l(Time.now, :format => :long) %>