module KramdownRFC

def self.dateattrs(date)
  begin
    case date
    when /\A\d\d\d\d\z/
      %{year="#{date}"}
    when Integer
      %{year="#{"%04d" % date}"}
    when String
      Date.parse("#{date}-01").strftime(%{year="%Y" month="%B"})
    when Date
      date.strftime(%{year="%Y" month="%B" day="%d"})
    when Array                  # this allows to explicitly give a string
      %{year="#{date.join(" ")}"}
    when nil
      %{year="n.d."}
    end
  rescue ArgumentError
    warn "*** Invalid date: #{date} -- use 2012, 2012-07, or 2012-07-28"
  end
end