Meio pseudo-código aproximado:
$records = /* SELECT * FROM `records` ORDER BY `entry_time` */;
$date = null;
foreach ($records as $record) {
$currentDate = date('Ymd', $record['entry_time']);
if ($currentDate != $date) {
printf('<h1>%s</h1>', date('Y-m-d', $record['entry_time']));
}
$date = $currentDate;
echo date('H:i', $record['entry_time']);
}