zero hour

"Zero hour" refers to the specific moment when a planned action or event is scheduled to begin or happen. It often signifies the exact time for a significant operation, such as a military strike, a military operation, or a critical decision point. Think of it as the "go" or "start" time in a carefully coordinated plan. In broader contexts, it can also mark the beginning of any major event, signaling that everything is ready to proceed exactly at that designated time.