zero hour

zero hour  {n.}
1. The exact time when an attack or other military action is supposed to start.
Zero hour for the bombers to take off was midnight.
2. The time when an important decision or change is supposed to come; the time for a dangerous action.
It was zero hour and the doctor began the operation on the man.
On the day of the championship game, as the zero hour came near, the players grew nervous.
Categories: noun time

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