It's sexist as it gives people an advantage based on their sex. This is unfair for: * women who are in pain more than one day a month because of their periods

It's sexist as it gives people an advantage based on their sex. This is unfair for: * women who are in pain more than one day a month because of their periods * men who have prostate troubles or other illnesses exclusive to men And it gives an unfair advantage to: * women who aren't in pain during their periods * women who have their period less than once a months (for example because of the Pill) The criterion to get the day off shouldn't be "are you women?" but "are you in pain?". They probably chose the former because they think it correlates that much.