sub iso_timestamp {
# create a string containing todays date and time in ISO format

  my $t = shift || time;

  my ($sec, $min, $hour,
      $mday, $mon, $year,
      $wday,$yday,$isdst) = localtime $t;
 
  $year += 1900;
  $mon += 1;
 
  return sprintf ("%04d" . "/"."%02d". "/"."%02d". " "."%02d". ":"."%02d". ":"."%02d",
		  $year,  $mon, $mday, $hour,  $min,  $sec);
		  
} # end of iso_timestamp