@gnurf: Apologies. It seems Query Posts doesn't offer this function after all.
I tried out YD Recent Posts widget as it offers a way of customising the date function, but for some reason it didn't display properly for me.
So I decided to opt for this code from Lesterchan's forums with PHP Code Widget and after checking the Codex documentation on formatting the_time, ended up with:
<?php $my_query = new WP_Query('showposts=4');
while ($my_query->have_posts()) : $my_query->the_post(); ?>
<?php
if (strlen(the_title('','',FALSE)) > 80) {
$title_short = substr(the_title('','',FALSE), 0, 80);
preg_match('/^(.*)\s/s', $title_short, $matches);
if ($matches[1]) $title_short = $matches[1];
$title_short = $title_short.'...';
}
else
{
$title_short = the_title('','',FALSE);
}
?>
<ul>
<li><a title="<?php echo the_title() ?>" href="<?php the_permalink() ?>"><?php echo $title_short ?></a><span><small><?php the_time('F jS, g:i a') ?></small></span></li>
</ul>
<?php endwhile; ?>
which seems to work ok for me - this particular snippet truncates the post title if it's too long.
I'm sure it's possible to build your own widget on the basis of this code rather than using PHP Code Widget as well.