Except in the UK, when it's normally transferred within a few seconds, or a maximum of two hours ("Faster Payments").
Have you ever had one take longer than zero time?
I have accounts with two banks (one for personal, one for joint finance with my wife) and FP makes that so easy to manage, if the joint account needs topping up I can do it in a minute or two on my laptop or phone.
I've had instances where it's taken more than hour, although it usually is as near instant as physically possible.