A date is what you stamp upon your design when you aim for ‘cool’.
Cool is a temporary thing, based on emotions and thoughts and ideas of the time in which it was made. More often than not, what’s cool is a taste of what people guess tomorrow will bring.
But tomorrow hasn’t happened yet. What we guess will look cool tomorrow is an assumption based on how we feel today.
Then once tomorrow is yesterday, its cool will look dated because how we feel has changed.
But making it look good regardless of immediate taste, fashion and style means that it’ll look cool no matter the day.
(Unless, of course, you deliberately want to tie it to a moment, for a moment.)