(posting on behalf of a user) I think the "use custom date" should actually be at the top of that part of the UI (right above the date picker/calendar), rather than the bottom. If a user is just typing in the date they want, then they have to move the mouse a bunch to then get down to the bottom. It's not intuitive that changing that date/time changes the selection at the bottom of the list, since all other parts of that "Snooze" sub-UI are static. I think a "set snooze" button that is more "within" the calendar/clock UI would be more intuitive to "do" the thing that's just been set in the date/time picker.