It seems pretty clear to me: > How precisely does Hetzner calculate the hourly billing? > The beginning of the hourly billing starts as soon as the product be

It seems pretty clear to me: > How precisely does Hetzner calculate the hourly billing? > The beginning of the hourly billing starts as soon as the product becomes available to you. So for a dedicated server you start paying once the server has been commissioned to you. You stop paying once you return it.