// If we have a day clean that too.
if ($context['view_week'])
{
if ($curPage['day'] > 31 || !mktime(0, 0, 0, $curPage['month'], $curPage['day'], $curPage['year']))
fatal_lang_error('invalid_day', false);
}
This can be "translated" to:
// If we have a day clean that too.
if ($context['view_week'] && !checkdate($curPage['month'], $curPage['day'], $curPage['year']))
fatal_lang_error('invalid_day', false);
Right?