It can never be opposite day. When ever you say "HEY IT'S OPPOSITE DAY!" the opposite would apply therefor it would not be opposite day. Also if you say "IT'S NOT OPPOSITE DAY!" the affect is not applied.
an ๐น indication of ๐ฆ the ๐ low ๐ intelligence, absence of ๐ฆ empathy, and ๐ devolution of ๐ฆ modern ๐ฅ man. ๐จ