The number everyone knows is 183. The question nobody asks until an auditor asks it for them is: what, exactly, is a day?
It sounds like pedantry. It is the whole game. Residency audits are not usually lost on the big blocks — the auditor and the taxpayer agree about January in Palm Beach and August at the lake. They are lost at the edges, in the twenty or thirty ambiguous days a travel-heavy year generates: the layovers, the midnight landings, the day trips, the drives through, the medical stays, the days that exist on no boarding pass. A snowbird whose self-count says 160 New York days and whose auditor-count says 187 didn’t mislay a month — they applied the wrong rules to the edges, thirty times.
This post is the day-counting law, plainly stated: the general rule, the exceptions that matter, and the edge cases that decide real cases.
The General Rule: Any Part of a Day Is a Day
Start with the rule that governs in New York and in most states with a statutory residency test: any part of a calendar day spent in the state counts as a full day in the state.
Not a majority of the day. Not an overnight. Any part. Under this rule:
- Land at LaGuardia at 11:48 p.m. → that calendar day is a New York day, all twelve minutes of it.
- Leave Manhattan at 6:05 a.m. → that day is a New York day too. An overnight stay therefore usually costs two counted days, not one.
- Drive from New Jersey to Connecticut across Westchester, never stopping → New York day.
- Step off the train in Stamford for a two-hour meeting → Connecticut day.
Notice the asymmetry this creates for the mover: the rule is generous to the state counting against you and stingy in your favor. There is no equivalent rule awarding you a Florida day for any twelve minutes in Florida — your Florida count is simply the days you were actually there, and on a travel day you can be “in” two states under two different counting postures at once. The conservative practice, and the one your advisor will tell you to adopt: count travel days against yourself on both boards. Treat the day you fly from Palm Beach to JFK as a New York day (it is, under the any-part rule) and don’t lean on it as a Florida day either. If your plan only works when the travel days break your way, your plan is too tight — build margin instead.
The Exceptions: Narrow, Specific, and Worth Knowing
The any-part rule has exceptions, and New York’s — the most litigated set — illustrate the shape they take everywhere: narrow, condition-laden, and strictly construed.
The travel exception. A day spent in New York solely in transit between two points outside New York does not count — the classic case being a connection at JFK between Florida and Europe, or driving through the state without conducting any business or personal affairs in it. The word doing the work is solely. Leave the airport for dinner, stop to see a grandchild, take a meeting at the gate — the exception evaporates and the day counts. If you rely on this exception, your records need to show the through-journey: both tickets, the timeline, no detours.
The medical exception. Days confined to a hospital or medical facility in the state for treatment are generally excluded from the statutory-residency day count. The exception covers the confinement — it does not stretch to outpatient visits, recuperating at the New York apartment after discharge, or accompanying a spouse to their appointments. Families dealing with a health crisis up north routinely assume the whole episode “doesn’t count.” Only the inpatient days do, and the documentation that proves it is the medical record itself.
Two warnings travel with every exception. First, they vary by state — the contours of Connecticut’s or Minnesota’s versions are not New York’s, and some states offer less. Second, exceptions are the auditor’s home turf: they are pleaded by taxpayers and disallowed on facts constantly. An exception you can’t document is an exception you don’t have.
The Edge Cases That Decide Real Audits
The undocumented day. The most important counting rule isn’t about presence at all — it’s about proof. In a statutory-residency examination, the practical burden is yours, and a day you cannot affirmatively place somewhere tends to be presumed against you. A three-week August gap with no transactions, no phone records, no anything, does not read as “not in New York” — it reads as twenty-one New York days unless you can show otherwise. This single rule converts sloppy record-keeping directly into tax liability, and it is why auditors open with your cell records rather than your recollection: the towers and the card swipes are the count.
The midnight problem. Days are calendar days, and calendar days end at midnight. The red-eye that departs at 11:55 p.m. and the one that departs at 12:10 a.m. produce different day counts. Nobody should schedule their life around this — but when you’re reconstructing a year, the timestamps matter, and when you’re planning a tight December, they’re worth a glance.
The “I wasn’t really there” day. Funerals, board meetings, closings, one-day emergencies — days that feel involuntary or trivial. The counting rules contain no hardship exception and no de minimis carve-out beyond the two above. The five “doesn’t really count” trips a year that every honest person mentally waives are, collectively, often the margin of failure.
The two-thresholds trap. Remember that your old state’s count and your Florida count are different boards with different stakes: the old-state board decides statutory residency at 183 days there; the Florida board supports your 183-day domicile evidence. The edges land differently on each — which is why the honest accounting tracks every day’s actual location, not a single running total.
The Operating Practice
Compressed to four habits:
- Count every partial day against yourself in the old state, including both travel days of every trip.
- Claim exceptions only with documents — through-tickets for transit days, medical records for confinement days.
- Leave no gaps. Every day of the year should be placeable somewhere with contemporaneous evidence; undocumented days belong to the auditor.
- Keep margin. If the count only clears with the edge cases breaking your way, change the calendar, not the counting.
The 183 everyone quotes is arithmetic. The “day” nobody defines is law. Audits are won by people who treated both seriously, in real time, all year.
Where Southbound Fits
Habit three is the one that can’t be done retroactively — and the one software does better than memory.
Southbound is an iOS app that records every day’s location automatically. It uses iOS’s significant-location-change system — not battery-draining GPS — to log each day as a Florida day or a non-Florida day as you live it, building the gap-free, contemporaneous record that the presumption-against-you rule punishes you for lacking. The Departure Budget keeps the running arithmetic visible as one number, and every day carries location evidence behind it.
The record lives in your own iCloud account — Southbound runs no servers and never sees your location history — and exports as a day-by-day CSV the moment your accountant or an examiner wants to argue about August.
Southbound is on the App Store, free during the early-adopter launch period. The counting rules don’t bend — but a year with evidence behind every single day doesn’t need them to.
This post is for general informational purposes only and does not constitute tax or legal advice. Day-counting rules, exceptions, and burdens of proof vary by state and are applied to specific facts. Work with a qualified tax attorney and CPA for advice specific to your situation.
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Published Jul 13, 2026