I couldn't figure out why posts with a defined date weren't appearing in my local Jekyll install. In the YAML matter, I'd written it as such:
date: 2005-01-24 12:00:36
Some more astute readers may already see the problem, but I was scratching my head late at night wondering why.
Turns out, you need to define the timezone:
date: 2005-01-24 12:00:36 +1000
It makes sense. If my base is UTC, that time I defined above wouldn't have happened yet, and I had configured Jekyll to not post items from the future. I mean, I'm not part of the USS Relativity's crew or anything.