Gwx 3 gold enemy status question

[pluskat]

Just after some general info about the workings of it
If I go to new York harbor 1 day before the USA enters
the war and stay until after midnight,then launch an
torpedo attack when the date says The USA is now
at war with Germany,will the ship losses still count
as neutral or as enemy losses.or do I have to go back
to base start a new patrol for that countries enemy
status to take effect.

thanks