The big 4-0 has long been a significant milestone. But for older Millennials – they love it when you call them “geriatric Millennials” – now plunging headfirst into their fifth decade on Earth, the expectations for how to behave and how to dress as they enter their middle age are somewhat blurred. For generations before, 40 was, well, old. Well old, in fact. Think dads with “proper” jobs, returning home in suits and ties. And yet, for 40-year-old men today, rocking beanies, hoodies and the latest sneakers, 40 still is – feels – quite young. Right?