ics_to_csv.rb

require 'icalendar'
require 'csv'
require 'optparse'

option={}
OptionParser.new do |opt|
  opt.on('-f', '--file=VALUE', 'iCal(ics) file path') {|v| option[:ics_file] = v}
  opt.on('-a', '--after=VALUE','after when: YYYY/mm/dd eg: -a 2015/11/22') {|v| option[:after_when] = v}
  opt.parse!(ARGV)
end

exit unless option[:ics_file]

csv_path = option[:ics_file].gsub(/\.[^.]+$/, '.csv')
puts "Converting... #{option[:ics_file]} -> #{File.basename(csv_path)}"

ical_src = IO.read(option[:ics_file])
cal = Icalendar.parse(ical_src, true)

if option[:after_when]
  after_when = DateTime.parse(option[:after_when])
  if after_when
    events = cal.events.select {|e| e.dtstart > after_when}.sort {|e1, e2| e1.dtstart <=> e2.dtstart}
  else
    puts "error"
    exit
  end
else
  events = cal.events.sort {|e1, e2| e1.dtstart <=> e2.dtstart}
end

CSV.open(csv_path, "wb:cp932") do |csv|
  csv << ['Start at','End at','Location','Summary','Description']
  events.each do |event|
    start_at = event.dtstart ? event.dtstart.strftime("%Y/%m/%d %H:%M") : ''
    end_at = event.dtend ? event.dtend.strftime("%Y/%m/%d %H:%M") : ''
    description = event.description ? event.description.gsub(/(\r\n|\r|\n)/, "\r\n") : ''
    row = [start_at, end_at, event.location, event.summary, description]
    #puts row.join(',')
    csv << row
  end
end

puts "Completed. #{csv_path}"

Converting from OSX Calender export file(ics) to CSV file(Japanese Shift-JIS CP932).
USAGE: $ ruby ics_to_csv.rb -f <ics file path> (-a <YYYY/mm/dd>)