Hand rolled ICS support

en.yml

# locales/en.yml
en:
  time:
    formats:
      ical: "%Y%m%dT%H%M%SZ"

ics.rb

# config/initializers/ics.rb
ActionView::Template.register_template_handler(:rb, :source.to_proc)
Mime::Type.register_alias "text/calendar", :ics

index.ics.rb

out = <<CAL
BEGIN:VCALENDAR
PRODID:-//I CAN HAZ COMPANY?//EN
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
CAL

@appointments.each_with_index do |appt, idx|
  out << <<CAL
BEGIN:VEVENT
DTSTART:#{l(appt.starts_at, format: :ical)}
DTEND:#{l(appt.ends_at, format: :ical)}
DTSTAMP:#{l(Time.now, format: :ical)}
UID:appointment#{appt.id}@#{request.host}
CREATED:#{l(appt.created_at, format: :ical)}
DESCRIPTION:#{appt.reason}
LAST-MODIFIED:#{l(appt.updated_at, format: :ical)}
LOCATION:
SEQUENCE:#{idx}
STATUS:#{appt.status_ical}
SUMMARY:#{appt.reason}
END:VEVENT
CAL
end

out << "END:VCALENDAR"

some_controller.rb

#...

  def index
    format.ics
  end
  
#...

You'll need to be mindful of timezone.

Wonderful gist! Thanks a lot :)