when is the eclipse, anyway?

This is bizarre. I'm going to be outside of St. Louis, and I thought I'd look up the time of the eclipse.

The NASA site says that totality will occur 18.17-18.19. Universal Time. And what is that in something humans understand? Well, here's a Universal Time to Central Daylight Time converter. 18, that's 6 pm if you're not in the army, converts to 1 pm local time. That sounds right; Central Time is 6 hours earlier than the UK, where UT is based, minus one for DST, makes five. So the eclipse will be around 1:18 pm, OK?

But wait! Here's the National Weather Service site, which is linked to from the NASA site, and it says 11:18 AM.

So which is it?