zero hour
US /ˈzɪroʊ ˈaʊər/
UK /ˈzɪroʊ ˈaʊər/

1.
jam nol, waktu mulai
the time at which a planned operation or event is scheduled to begin
:
•
The troops were ready for zero hour, awaiting the command to advance.
Pasukan siap untuk jam nol, menunggu perintah untuk maju.
•
The launch countdown began, signaling that zero hour was approaching.
Hitungan mundur peluncuran dimulai, menandakan bahwa jam nol semakin dekat.