Depends. Technically any day that you set foot in the state of avoidance counts. Also it *might* count as a day if you're in the middle of a trip and fly into said state. Regional pilots who do most of their actual flying within a certain state can end up paying taxes there even if resident in another state (common in the turboprop days).

But as far as your residence state goes... you do NOT have to spend six months there, you only have to AVOID reaching six months in the avoidance state. As long as you've reasonably established residence (local address, DL, car registration, library card, tax filing) then there's rarely any minimum annual time requirement, although a couple states might have a very minimal requirement. Back in the day when Alaska paid a dividend to residents some military people would buy an acre and set up residency to collect their annual dividend. IIRC they had to visit their property once per year, typically a fishing trip and check in at the county court house to document their presence.

But again generalities, get professional advice for the states in question (some have bilateral agreements which can alter the rules).