use Memories;
my $it = Memories::Photo->retrieve_all;

my $thing = $it->first;
do {
    print $thing->title, "   $tag\n";
    my $tag = "date:".$thing->shot->ymd;
    $thing->add_to_system_tags({tag => Memories::SystemTag->find_or_create({name
    =>$tag}) });
} while $thing = $it->next;