Recently one of the customer asked whether release management offers a way by which they can approve a deployment for a pre-configured time. This means that customer should be able to approve the deployment now but should be able to specify the time at which deployment should start.
We have a feature called "deferred approval" for exactly the same problem and a lot of customers (including me in our dogfooding) use that pretty often. This feature enables you to specify the time (along with the time-zone) at which the deployment should start while you are approving a deployment. See the below image for more details.