class AWS::S3::Request

def signing_string_date
  # if a date is provided via x-amz-date then we should omit the
  # Date header from the signing string (should appear as a blank line)
  if headers.detect{|k,v| k.to_s =~ /^x-amz-date$/i }
    ''
  else
    headers['date'] ||= Time.now.rfc822
  end
end