An idiom referring to a moment very close to a deadline
or a climax
. The penultimate
This is the moment of last chances or the moment where it's just too late.
The moment when an application is usually handed in, tax forms are mailed out (with prayers) and class papers are dropped on the teachers desk.
The moment to a finale as the 11th hour is to the 12th hour.
Please see under the wire for a similiar idiom.
Part of the American Idioms project on everything2