Date ranges, typically for shows ...

date_helper.rb

module ActionView
  module Helpers
    module DateHelper
      # returns a date range in English
      #  July 3-5, both days are the same month
      #  July 3 - August 5, days are different months
      #  December 20, 2010 - January 10, 2012, days are over a year apart
      def date_range_in_words(start_date, end_date)
        # convert to date
        start_date = start_date.to_date if start_date && start_date.respond_to?(:to_date)
        end_date = end_date.to_date if end_date && end_date.respond_to?(:to_date)
        # swap poorly ordered values
        start_date, end_date = end_date, start_date if start_date && end_date && end_date < start_date
        # different dates
        if start_date && end_date && start_date != end_date
          # different year, more than one year apart, always include year
          # ends next year, but same month or earlier month
          if (end_date.year - start_date.year > 1) || (start_date.month <= end_date.month && start_date.year != end_date.year)
            "#{start_date.strftime('%B')} #{start_date.day.ordinalize} #{start_date.year} - #{end_date.strftime('%B')} #{end_date.day.ordinalize} #{end_date.year}"
          elsif start_date.month != end_date.month
            "#{start_date.strftime('%B')} #{start_date.day.ordinalize} - #{end_date.strftime('%B')} #{end_date.day.ordinalize}"
          else
            "#{start_date.strftime('%B')} #{start_date.day.ordinalize} - #{end_date.day.ordinalize}"
          end
        # one date
        elsif date = (start_date || end_date)
          "#{date.strftime('%B')} #{date.day.ordinalize}"
        else
          ""
        end
      end
    end
  end
end

date_helper_spec.rb

require 'spec_helper'

describe ActionView::Helpers::DateHelper do
  include ActionView::Helpers::DateHelper
  context "date_range_in_words" do
    it "nils" do
      date_range_in_words(nil, nil).should be_blank
    end
    it "start only" do
      date_range_in_words(Date.new(2001, 2, 3), nil).should == "February 3rd"
    end
    it "end only" do
      date_range_in_words(nil, Date.new(2001, 2, 3)).should == "February 3rd"
    end
    it "same date" do
      dt = Date.new(2001, 2, 3)
      date_range_in_words(dt, dt).should == "February 3rd"
    end
    it "same time" do
      dt = Time.new(2001, 2, 3, 4, 5, 6)
      date_range_in_words(dt, dt).should == "February 3rd"
    end
    it "same date but not same time" do
      dt1 = Date.new(2001, 2, 3)
      dt2 = Time.new(2001, 2, 3, 4, 5, 6)
      date_range_in_words(dt1, dt2).should == "February 3rd"
    end
    it "different days same month" do
      dt1 = Date.new(2001, 2, 3)
      dt2 = Time.new(2001, 2, 4)
      date_range_in_words(dt1, dt2).should == "February 3rd - 4th"
    end
    it "wrong order" do
      dt1 = Date.new(2001, 2, 3)
      dt2 = Time.new(2001, 2, 4)
      date_range_in_words(dt2, dt1).should == "February 3rd - 4th"
    end
    it "different months" do
      dt1 = Date.new(2001, 2, 3)
      dt2 = Time.new(2001, 3, 3)
      date_range_in_words(dt1, dt2).should == "February 3rd - March 3rd"
    end
    it "different years" do
      dt1 = Date.new(2001, 12, 29)
      dt2 = Time.new(2002, 1, 3)
      date_range_in_words(dt1, dt2).should == "December 29th - January 3rd"
    end
    it "different years but same month" do
      dt1 = Date.new(2001, 1, 29)
      dt2 = Time.new(2002, 1, 3)
      date_range_in_words(dt1, dt2).should == "January 29th 2001 - January 3rd 2002"
    end
    it "different years two years apart" do
      dt1 = Date.new(2001, 1, 29)
      dt2 = Time.new(2003, 2, 3)
      date_range_in_words(dt1, dt2).should == "January 29th 2001 - February 3rd 2003"
    end
    it "different non-consecutive years" do
      dt1 = Date.new(2001, 12, 29)
      dt2 = Time.new(2003, 1, 3)
      date_range_in_words(dt1, dt2).should == "December 29th 2001 - January 3rd 2003"
    end
  end
end