This is literally anytime, anywhere though. Do just not meet up with their friends? You can go to dinner, get drinks, go hiking, play sports, bike, ski, sunbathe, play videogames and many more things in single-sex groups without raising an eyebrow. The real classic for men of a certain persuasion from a western cultural POV is golf right?
I think there's some strange cultural hangup I'm missing where the entire place needs to be single-sex.