Hey, all you New Yorkers!

Have any ideas ever been put forth on how long it WOULD take to evacuate NYC?

Just a random for-instance: Terrorists have planted a nuclear bomb somewhere in NYC, and it is set to go off in seven days if a ransom isn't paid. The news is immediately transmitted to the public, not kept secret until two hours before know-it-all authorities realize they can't get to the bomb to stop it.

I'm supposing good weather, with no other disasters getting in the way.