When is a cooking lesson worth the same as a dental cleaning? Or a tree stump removal worth the same as a hand-hammered silver bracelet? When both services are provided as part of a time exchange, or time bank. Time banking isn’t a new concept–it’s been around at least since the late 1980s. But now that most people’s wallets are looking more threadbare than at any time since the Great Depression, this creative concept is catching on.