I've implemented this in elisp, here: https://github.com/tjim/nevermore/blob/master/nm.el#L745

Snooze has come up a repeatedly on this list. Maybe it would make sense to build it in to notmuch?

Of course, it can be built on top of notmuch so it's not necessary to bake it in. But there are other features in notmuch of which you could say the same, e.g., excluded tags.

The benefit of building it in would be a common interface/implementation that all UIs could use.