Japanese night carrier doctrine changes opening-strike options

What changes if Japan develops carrier night-fighting doctrine comparable to Britain's by 1939?

Japan gains new opening-strike options, especially at Pearl Harbor, but the development would not remain invisible to Britain and other observers.

A whole-fleet night doctrine would differ from the historical Japanese emphasis on cruiser and destroyer fighting. Folding carrier aviation into that system could support an overnight Pearl Harbor strike instead of the familiar Sunday-morning attack. Experience gained by 1939 would probably make the force still more capable by 1941. The development would not remain invisible, however, because foreign naval attaches could infer night-operating equipment from the location and shape of fittings aboard Japanese ships.