Calculators · guides · the app
Resources
Everything on this site, in one place: the calculators that do the arithmetic, the guides that explain the rules, and the app features that make the counting automatic.
Interactive tools
Free, no sign-up — the arithmetic behind the rules, done for you.
Visa checker
Entry requirements for 199 passports across every destination — visa-free days, eTA, e-visa, visa on arrival, visa required.
Schengen 90/180 calculator
Enter your trips; get days used in the rolling window, your latest safe departure date, and overstay warnings.
Substantial presence test calculator
The IRS weighted 31-day / 183-day test across three years of US presence.
183-day calculator
The bright-line day count shared by the UK, Canada, India, and US states.
Guides
The concepts and per-jurisdiction detail behind the numbers.
Tax residency 101
What tax residency is, the three shapes of a residency test, and why the burden of proof makes tracking matter.
Tax tracking by jurisdiction
Day-count rules for all 50 states, DC, and the Canadian provinces — 64 jurisdiction guides with official links.
Visas by passport
The index of all 199 per-passport requirement pages.
In the app
What Day31 does on your iPhone so none of this is manual.
Automatic day counting
The timeline builds itself from your location — no manual check-ins, works offline.
Limit alerts
Schengen 90/180, substantial presence, and per-state thresholds watched with warnings before you cross.
Export for your accountant
Day-count summaries per jurisdiction for any reporting period — for accountants and border officers.
Visa data current as of February 2026. Calculator rules reviewed for 2026. Entry and tax rules change — always confirm with the official sources linked from each page.