http://www.combinedfleet.com/hiei2.htm
2 December 1941:
940 miles N of Midway Island. Nagumo’s Force receives the coded signal "Niitakayama nobore (Climb Mt. Niitaka) 1208" from the Combined Fleet. It signifies that X-Day hostilities will commence on 8 December (Japan time).
That same day, the oilers refuel
BatDiv 3/1's HIEI and KIRISHIMA.
7 December 1941: The Attack on Pearl Harbor:
At 0630, BatDiv 3/1 launches Type 95 Nakajima E8N "Dave" two-seat reconnaissance floatplanes to patrol south of the Striking Force. CruDiv 8 also launches picket floatplanes.