Hello Laurent,
It seems like we do not enforce the date to get hidden on timeless because this is actually the design of it. If you hide the date, then there won't be any "calendar" design on the left. If you don't want those calendar, why not switch to the wireframe theme?
If you still need to use timeless but remove the date, here's what you can do, edit the file /components/com_easyblog/themes/timeless/blogs/latest/default.main.php and remove the codes below,
[gist]
<div class="eb-post-calendar">
<div class="eb-post-calendar-m">
<?php echo strtoupper($post->getDisplayDate($this->params->get('post_date_source', 'created'))->format(JText::_('M'))); ?>
</div>
<div class="eb-post-calendar-d">
<?php echo $post->getDisplayDate($this->params->get('post_date_source', 'created'))->format(JText::_('d')); ?>
</div>
</div>
[/gist]