Add date and/or time besides latest posts

Hi everyone,

I am a WordPress newbie, I really begin to use it and I try to make some custom stuff for my website.

I hope someone could help me to reach my goal.
I have a function on my sidebar which displays latest posts :

<li id="recent-posts" class="widget">
		<h2>Recent posts</h2>
			<ul>
				<?php wp_get_archives('type=postbypost&limit=10'); ?>
   			</ul>
		</li>

And I would like to customize it by showing the date or the hour of the post. If post hasn’t been written today, I want to show date (ex: 11/21) and if it has been written the same day user visits the site, I want to show hour, example 11:21

Does anyone has an idea how to do so ?
Thanks in advance.