class RDoc::Parser::ChangeLog

def group_entries entries
  @time_cache ||= {}
  entries.group_by do |title, _|
    begin
      time = @time_cache[title]
      (time || parse_date(title)).strftime '%Y-%m-%d'
    rescue NoMethodError, ArgumentError
      time, = title.split '  ', 2
      parse_date(time).strftime '%Y-%m-%d'
    end
  end
end