How can I send out my newsletters on a timed schedule?

We operate 9 moderated discussion lists that we send as
announce-only type of lists. I'd
like to release these at certain times of the morning (say from 3
am to 9 am).

I haven't seen anything about this in the docs (yes, I've read the
manual many times). I do not consider the "Prime Time" setting to
be a solution for this.

Any help?

Adam