В прошлой записи я упоминал о баге(особенности) функции strtotime(), все же есть workaround:
<?php
date_default_timezone_set('Europe/Moscow');
$today = strtotime('28-04-2013'); // 28-04-2013, воскресенье
$thisWeek = strtotime('last sunday +1 day', $today);
$lastWeek = strtotime('-1 week', $thisWeek);
$nextWeek = strtotime('+1 week', $thisWeek);
echo 'last week - '.$lastWeek.' / '.date('d-m-Y H:i\n',$lastWeek);
echo 'this week - '.$thisWeek.' / '.date('d-m-Y H:i\n',$thisWeek);
echo 'next week - '.$nextWeek.' / '.date('d-m-Y H:i\n',$nextWeek);
результат работы:
last week - 1365969600 / 15-04-2013 00:00
this week - 1366574400 / 22-04-2013 00:00
next week - 1367179200 / 29-04-2013 00:00