Since I use my calendar since several years the size of the file has grown to more than 1.5 MB; which starts to slow down some applications (especially on my PDA). So I looked arround how to get rid of old data ...

On one of the Ximian-Lists a similar problem was discussed a while ago. There Kyle Davenport published a short perl-script, which can be used for this: it just removes all entries, except the ones for the year specified:

#!/usr/bin/perl 
# filter out old vcalendar entries
$DATA = `cat mycalendar.ics`;
$DATA =~ s/(.*?)BEGIN:VEVENT/BEGIN:VEVENT/s; 
print "$1"; 
while ( $DATA =~ /BEGIN:VEVENT/ ) { 
 $DATA =~ s/(BEGIN:VEVENT.*?END:VEVENT)(.*)/$2/s; 
 if ( grep /DATE:2007/,($1) ) { print "$1\n"; } 
} # end of [while]
print $DATA;