We hit the Debt Limit...
in May of 2013.
Treasury has been juggling stuff the last five months to stay under the debt ceiling, and October 17th is an estimate of the fullest extent of that juggling. There is no legal point of expiration... no mandated midnight hour. The limit is practical, not legal. Treasury will indeed start defaulting on stuff soon, but this is not like the end of a federal fiscal year that, as a matter of law, happens at 12:00:00 on a certain date.
Making CNN's count-down clock to debt limit (calibrated to the second, mind you) among the very dumbest things I've ever seen.
Politically advantageous for us, so I am not irate. But it deserves mockery.
This does not diminish the seriousness of the real world situation, at all. It is just atrocious journalism. It's like starting a 28 day countdown clock (calibrated to the second) for when someone will die from a hunger strike because some doctors gave 28 days as their best estimate. Starving to death is plenty serious, but it isn't precise.