How to customise calendar week view's day title?
Y rectify like this and that seems good for me:

function template_preprocess_calendar_week(&amp;$vars) {
$min_date = clone $vars['view']-&gt;date_info-&gt;min_date;
foreach ($vars['day_names'] as &amp;$cell) {
 $cell['date'] = $min_date-&gt;format('j');
 $cell['data'] = $cell['data'] . ", " . $cell['date'];
 $min_date = $min_date-&gt;modify('+1 day');
}
}