Longer answer, they're usually overnight, the transaction goes out one day and funds are available the next (to the bank anyway). In some cases, there's same day stuff if you hit the early window, but that takes a cooperative bank. Retail wise, they can take up to 2 business days if you try to do it at a small bank with a correspondent relationship to a real bank in alaska.

But when you see 4 or 5 days, it's because the bank is holding access to the funds because the transaction is reversible. 3 days is the window for things like NSF and incorrect account numbers, but in the case of unauthorized stuff, it's 90 days. Frauds can claw back even farther.