Under many residency rules, any part of a day in a place counts as a full day there. New York's tax department says it plainly: "Any part of a day is a day for this purpose." So a morning flight out or a lunch stop can each add a day. There are exceptions, so check the rule that applies to you with a tax professional.
Two different "183-day rules"
People say "the 183-day rule" for two separate tests.
| Test | Who it's about | The day count |
|---|---|---|
| State residency (New York, for example) | People domiciled elsewhere who keep a home in the state | New York treats you as a resident if you keep a permanent place of abode there for substantially all of the year and spend 184 days or more in the state. |
| Federal substantial presence test (IRS) | People who aren't US citizens or green card holders | At least 31 days this year, and 183 days over three years counting all days this year, a third of last year's days and a sixth of the year before. |
Other states have their own versions. Many use a similar "more than 183 days plus a home" test, but the details differ.
How a day is counted
The key word is presence, not nights. New York's tax department puts it in one line: "Any part of a day is a day for this purpose." The IRS says you are treated as present on any day you are physically present in the country.
| What happened (example) | How it usually counts |
|---|---|
| You drove into New York for lunch and left at 3 PM | A New York day, under New York's rule |
| You flew out of New York at 7 AM | A New York day |
| You were in New Jersey and New York on the same date | Each state applies its own rule, so one date can count in both |
| A layover under 24 hours, between two places outside the US | Not counted for the IRS test (an exception) |
There are other exceptions (for example, some commuters from Canada or Mexico, and certain visa holders for the IRS test), so check the exact rule that applies to you.
Why a day-by-day record matters
If a tax department asks where you were, you're the one who has to show it, and memory doesn't hold up well a year later. Practitioners commonly point to records like receipts, calendars and phone location history. A record kept as you go, with where each entry came from, is easier to stand behind than one rebuilt from a credit card statement.
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Coming soon to the App StoreQuick answers
Does part of a day count as a day?
Under many state rules, yes. New York's tax department says any part of a day is a day for its residency count. The IRS treats you as present on any day you are physically in the US, with some exceptions.
Is the 183-day rule the same in every state?
No. Each state sets its own test, and the federal substantial presence test is a separate rule with its own weighted formula.
Does Statecount tell me if I'm a resident?
No. Statecount keeps records. It is not tax or legal advice. A tax professional can tell you how the rules apply to you.
Sources
- New York State Department of Taxation and Finance: definitions of resident, nonresident and part-year resident
- IRS: Substantial presence test
- IRS Publication 519: U.S. Tax Guide for Aliens
Statecount keeps records. It is not tax or legal advice. Rules change and have exceptions: confirm with a tax professional.
Published 2026-10-12.