Case saturday or sunday as working day

[aidar87]

Hi guys, could you advise how can I set Saturday or Sunday as working day only in some cases( not always)?
The special day evaluator requires return an array of opening intervals.

This doesn't work:
new SpecialDay(Days::SATURDAY, function (\DateTime $date) {
if ('2015-05-29' === $date->format('Y-m-d')) {
return [['00:00', '23:59:59']];
}
return ;
});