Header by date?

My blog’s main headers are by date. I’m just using a basic loop:

<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>
<h1><?php the_time('F j, Y') ?></h1>
<h2><?php the_title(); ?></h2>
<?php the_content(); ?>
<?php endwhile; ?>
<?php endif; ?>

This works fine for me except that if there’s more than one post on the same day, that <h1> repeats. How can I get it to only show the date <h1> once for a day (before the first post?