If it's just Date semantics, that's a fairly insignificant amount of copying. I'm not saying there isn't superficial similarity. But just look at the fact that

If it's just Date semantics, that's a fairly insignificant amount of copying. I'm not saying there isn't superficial similarity. But just look at the fact that Javascript until ES6 has lacked a useful `class` keyword, without which you can't even write a Java program. I suppose "functional" is in the eye of the beholder. I see it in terms of what a language allows you to do, not what it prohibits you from doing. You can absolutely choose not to use shared mutable state.