In theory EU and the Euro area are the same, because the TFEU says so. But in practice it's more complicated than this as Danes negotiated and opt-out clause during the negotiation of the treaty of Maastricht, and even though such clause isn't open to new entrants, in reality nothing prevents negotiations to eventually lead to such an outcome.

The case of Sweden is interesting though, they don't have an opt-out clause so they are obligated to adopt the Euro eventually, but they exploited a loophole by not joining the newest version of European Exchange Rate Mechanism after the 1999, which prevents their entry in the Euro.