United States: how days are counted

At a glance

The test: Substantial presence test (IRC §7701(b)(3)): at least 31 days this year, and a weighted total of 183 days or more over three years.
Period: Calendar year, 1 January to 31 December, plus the two years before it.
What counts as a day: Any day you are physically present in the 50 states, DC or US territorial waters at any time during the day.

The rule

A person who is not a US citizen is treated as a resident alien for US tax if they meet the green card test or the substantial presence test for the calendar year (IRS Publication 519).

Substantial presence test: present on at least 31 days in the current year, and the sum of current-year days, one-third of last year's days and one-sixth of the year before's days equals or exceeds 183. IRS example: 120 days in each of three years gives 120 + 40 + 20 = 180.

A day counts if you are physically present at any time during it. The United States means the 50 states, DC and territorial waters, not US territories or airspace. Some days are excluded, such as regular commuting from Canada or Mexico, under 24 hours in transit between two foreign places, foreign vessel crew, a medical condition, and exempt individuals.

Closer connection exception (§7701(b)(3)(B)): a person who meets the test but is present fewer than 183 days in the current year, keeps a tax home in a foreign country and has a closer connection to it than to the US is not treated as meeting the test. It does not apply if a green card application is pending.

States set their own rules. Many states with a day test combine a permanent home in the state with more than 183 days: for example Connecticut, Massachusetts, New Jersey and Pennsylvania. Georgia, Maryland, Minnesota and Nebraska use 183 days. Oregon uses more than 200, Idaho more than 270, North Dakota more than 7 months, New Mexico 185 full 24-hour days. Some states only presume residence from days.

New York State and City: a person not domiciled in New York who keeps a permanent place of abode there and spends more than 183 days in New York in the tax year is a resident individual (Tax Law §605(b)(1)(B)). Any part of a calendar day counts, except presence solely to board a carrier out of the state or while travelling through it (20 NYCRR 105.20(c)). The city applies the same test.

How Atrium counts it

Atrium counts every day you record in the US, including the arrival day and the departure day. A day counts if any part of it falls in the US.

Atrium does not remove excluded days. Transit, commuter, medical, student and other exempt days all count. Your adviser decides whether any exclusion, the closer connection exception or Form 8840 applies. This can count more days than the law requires.

For the two earlier years Atrium uses the totals from your recorded trips or the totals you enter. If a year is unknown it uses 365 days, which gives the earliest, most cautious reading.

Atrium shows days left before both conditions are reached: 31 days, and the weighted 183. It works in whole numbers: 6 times this year's days plus 2 times last year's plus the year before's, compared with 1,098. If you say you are a US citizen or green-card holder, it does not show these days.

For states with a day condition, Atrium counts the days from your trips and assumes you have a home there, the strict reading. It shows the days left to that state's condition, under the name of the state's test. For New York it drops the line if you say you have no home there. It counts New Mexico only in full 24-hour periods.

What catches people out

A short visit still counts. Landing at 23:00 and leaving the next day is two US days.
Earlier years carry forward. 122 days in each of three years gives 122 + 40.67 + 20.33 = 183 exactly. In whole numbers, 6 x 122 + 2 x 122 + 122 = 1,098.
The 31-day condition is separate from the weighted 183. Both are needed.
A day can count in a state and in the federal test. States count days on their own terms, and several use abode as well as days.
In New York, arriving at or leaving from your own New York home counts as a day even if you are there for a few hours. Only boarding a carrier out, or travelling through, is disregarded.

Cases

Decided case

Matter of Zanetti: 26 part days by private jet

New York Division of Tax Appeals, Administrative Law Judge · 2013 · DTA No. 824337 (23 May 2013) Source

For 2006, John Zanetti agreed he was in New York on 167 whole days, outside the state on 172 whole days, and that he kept a permanent place of abode in Manhasset. On 26 other days he arrived or left by private jet and stayed at or left from that home. He argued a day means 24 hours, so those days were not New York days. The judge applied the part-of-a-day rule, counted all 26 and sustained the tax and penalties.

In New York a few hours in the state is a full day. Atrium counts the same way. The decision follows Matter of Leach v. Chu (3rd Dept 1989), cited in it.

Official ruling

Rev. Proc. 2020-20: days kept in the US by COVID-19 travel limits

Internal Revenue Service (revenue procedure, not a court case) · 2020 · Rev. Proc. 2020-20, 2020-20 I.R.B. 801 (11 May 2020) Source

The IRS gave relief to some nonresident individuals who, but for COVID-19 travel disruption, would not have been in the US long enough in 2020 to meet the substantial presence test. They could use the medical condition exception to exclude up to 60 consecutive days in the US, starting any day from 1 February to 1 April 2020, which each person chose.

Exclusions are real but narrow and need a claim. Atrium counts every recorded day, so an excluded day still counts in Atrium until your adviser applies the rule.

Sources

Based on the sources above, last reviewed on 2026-10-04. Educational content, not tax advice. Atrium counts days; whether those days make you resident is for you and your adviser to decide.

Count your days in Atrium