@Horntoad has it right. The server is set to GMT/UTC timezone. Basically, we needed the server set to a timezone that didn't change with the seasons. The US time zones are constantly switching back and forth for daylight savings time, while the UTC timezone stays fixed year round. That's preferable from a programming point of view.
That's why each day begins at 7:00pm CDT.
I have thought much about the idea of changing that to a different timezone, something that is more US-centric, but I never really considered it that high of a priority. I kind of like the new day beginning in our evening, so we can see the next day's content early.
