California does not use a fixed day count. It weighs a closest-connections and domicile test instead. Here is what California would need to see before an exit claim survives an audit.

California is the state practitioners and community forums most consistently describe as the toughest to leave. FTB residency audits concentrate on high earners whose departure date lines up with a liquidity event, business sale, or large stock vesting; a claimed move date of late December followed by a January capital gain is a classic trigger. For filed part-year or nonresident returns, FTB has four years to assess. If no California return was ever filed for a year FTB believes you were a resident, there is no statute of limitations at all (R&TC §19057(a)), which is what makes silent nonfilers, not honest part-year filers, FTB's highest-risk targets.