"Daily" is actually "24 hours after first message in notify queue"

I think Message Digest operates a bit counterintuitively, with respect to the "Daily" digest notifier.

As a user, I'd expect that I'd get a digest in the evening (possibly at a significant time, like midnight, but not necessarily) of everything done on the site that day. Instead, the notifier calculates the day as "24 hours from the first message in the notifier queue", which really isn't the same thing.

In terms of UX and expectations, I think it makes sense for the notifier to be truly *daily*, which doesn't quite mean "after 24 hours."

Thoughts?