"Half-year plus one day" might work for RESIDENCY purposes, but establishing one's DOMICILE for tax purposes is more complicated. I was an Income Tax Auditor for NY State back in the 90's, and I was assigned to the "snowbird" unit on Long Island. We collected lots of tax revenue from people who had a winter residence outside of NY (usually Florida), but maintained a permanent place of abode in NY and had NOT changed their domicile to FL. Changed their tax filing status from "Non-Resident" to "Resident" unless they could meet the burden of proof in establishing a change of domicile; most couldn't because they still had business and other ties to NY.