Following changes to lib/TWiki/attach.pm allows time/date processing:

Add after

use strict; 
use Assert; 

use TWiki::Time; 

and add before

    # I18N: Site specified %ATTACHEDIMAGEFORMAT% or %ATTACHEDFILELINKFORMAT%,
    # ensure that filename is URL encoded - first $name must be URL.
    $fileLink =~ s/\$name/$fileURL/;
    $fileLink =~ s/\$name/$attName/;

    my $fileext = $attName;
    $fileext =~ s/(.*\.)*([^.]*)/$2/;
    $fileLink =~ s/\$fileext/$fileext/;

    if (defined $att->{date})
    {
      my $date = $att->{date};
      use Time::localtime;
      my ($seconds,$minutes,$hours,$day,$mo,$ye,$wday,$ydat,$isdst) = gmtime($date);
      #require TWiki::time;
      $fileLink =~ s/\$date/TWiki::Time::formatTime( $date || 0)/gei;
      $fileLink =~ s/\$seconds/TWiki::Time::formatTime( $date || 0, "\$seconds")/gei;
      $fileLink =~ s/\$minutes/TWiki::Time::formatTime( $date || 0, "\$minutes")/gei;
      $fileLink =~ s/\$hours/TWiki::Time::formatTime( $date || 0, "\$hours")/gei;
      $fileLink =~ s/\$wday/TWiki::Time::formatTime( $date || 0, "\$wday")/gei;
      $fileLink =~ s/\$day/TWiki::Time::formatTime( $date || 0, "\$day")/gei;
      $fileLink =~ s/\$month/TWiki::Time::formatTime( $date || 0, "\$month")/gei;
      $fileLink =~ s/\$mo/TWiki::Time::formatTime( $date || 0, "\$mo")/gei;
      $fileLink =~ s/\$year/TWiki::Time::formatTime( $date || 0, "\$year")/gei;
      $fileLink =~ s/\$ye/TWiki::Time::formatTime( $date || 0, "\$ye")/gei;
    }

After this change, following attachment example is possible:
On TWIki Site:

   * Local ATTACHEDFILELINKFORMAT = |$year-$mo-$day|Effort        |[[%ATTACHURL%/$name][%ICON{$fileext}% $name]]| received from company xy |

Simple enhancement with nice effects, good enough to add to the next twiki version?

-- TWiki:Main/SaschaVetter - 18 Aug 2008

Sascha, I just discovered this because it was waiting for feedback, but had no-one in the "Waiting For" field. That's a sort of limbo; nothing will happen to reports in that state. I changed it to "New". The code is fine, but this should really have been raised as a feature proposal and we are now in feature-freeze for Foswiki 1.0.0.

I have created AddTimeFeaturesToAttachmentLinks for you.

• CrawfordCurrie - 24 Nov 2008

Going ahead with this, with some changes:

• Uses Foswiki::Time::formatTime() to expand any of the defined date/time tokens
• Uses Foswiki::expandStandardEscapes() to handle $n, $comma, $lt, etc.

Added unit tests.

-- GeorgeClark - 26 May 2012