class Icalendar::Values::Date

def <=>(other)
  if other.is_a?(Icalendar::Values::Date) || other.is_a?(Icalendar::Values::DateTime)
    value_ical <=> other.value_ical
  else
    nil
  end
end

def initialize(value, params = {})
  params.delete 'tzid'
  params.delete 'x-tz-store'
  if value.is_a? String
    begin
      parsed_date = ::Date.strptime(value, FORMAT)
    rescue ArgumentError => e
      raise FormatError.new("Failed to parse \"#{value}\" - #{e.message}")
    end
    super parsed_date, params
  elsif value.respond_to? :to_date
    super value.to_date, params
  else
    super
  end
end

def value_ical
  value.strftime FORMAT
end