- strtotime: documentation ( source)
<?php
$date = new DateTime();
$date->setTimezone(new DateTimeZone('Europe/Minsk'));
echo $date->format('Y-m-d H:i:s');
echo '<br />';
echo strtotime($date->format('Y-m-d H:i:s'));
echo '<br />';
echo strtotime($date->format('Y-m-d'));