Every stay-limit calculation on EuroVisaCalculator traces back to a specific government publication. Not a summarized version of one, not a third-party aggregator, and not a chatbot's best guess. Here is how we source that data and how we keep it accurate as visa regimes change.
We cite official government sources for every rule
Each destination in EuroVisaCalculator is backed by a dedicated data file that references the exact regulation, statutory instrument, or official guidance page it comes from. Every passport rule in the app carries a citation to that source, so the results you see trace back to a specific legal text or official Ministry of Foreign Affairs webpage.
For the Schengen Area, two regulations work together. The Schengen Borders Code (Regulation (EU) 2016/399) sets the conditions of entry for third-country nationals and defines the 90-days-in-any-180-day-period limit itself. This is the legal basis for the rolling-window calculation at the center of the app. Alongside it, Regulation (EU) 2018/1806, Annexes I and II, sets out which nationalities require a visa and which travel visa-free. That regulation is the source for every passport's baseline access category.
Where a nationality's access depends on an airport transit visa, we cite the Schengen Visa Code (Regulation (EC) 810/2009) Annex IV common list, plus the Visa Code Handbook Annex 7B for the additional, member-state-specific requirements that individual countries impose beyond the common EU list.
The same approach carries through outside Schengen. The UK's Standard Visitor route and Electronic Travel Authorisation requirements are sourced from GOV.UK and the Immigration Rules' Appendix Visitor Visa National List and Appendix ETA National List. Ireland's non-visa-required nationality table comes from the Irish Naturalisation and Immigration Service. Türkiye's rules, including several nationality-specific exceptions to the standard 90/180 window, are sourced from Türkiye's e-Visa system and its published bilateral arrangements. Montenegro, Serbia, Bosnia and Herzegovina, Kosovo, North Macedonia, and Albania each cite their own national visa legislation. Cyprus, an EU member outside the Schengen border-free area, is governed by the same Regulation 2018/1806 as Schengen, so its rules cite that regulation directly rather than a separate national source.
Sometimes information on who is permitted visa-free entry to a jurisdiction is not colocated with information on the duration limits afforded to visitors with visa-free eligibility. In certain cases, official sources for such stay length limits are unavailable, so we may default to using widely-reported information from other sources. In such cases, we make it very clear when no official source is available for citation.
Sources are checked regularly
A link alone doesn't tell you whether the underlying rule is still accurate. Alongside every citation, we track the date each source was last confirmed current. When a rule changes, that date is what tells us a citation needs a second look.
We also keep a stable "parent" policy-page link alongside every direct document citation, since government sites reorganize and PDFs move. If a direct document link ever breaks, we can fall back to the parent page rather than lose the reference entirely.
We watch for regime changes
Visa regimes change. A country adjusts a reciprocal exemption, the EU updates Annex I or Annex II, a nationality is added to an airport transit list, or ETIAS shifts from planned to mandatory. We revisit our sources on an ongoing basis, and when a change affects an existing rule, we update it and republish.
Whether automated or manually, all sources are regularly confirmed to be accurate, and all candidates for change are reported and eventually approved by a human. While our checks are frequent, policy changes in a nation's visa regime can occur without warning. EuroVisaCalculator is inherently reactive to these changes and can sometimes be out of date if a new accuracy check has not yet been issued. For this reason we recommend users follow our citation links to confirm the official source documentation themselves.
We've written about the mechanics of the underlying rules in more detail elsewhere, and comparing those posts against the government texts we cite is one way to check our work yourself:
The Schengen 90/180 Rolling Window, Explained Visually illustrates how the rolling window itself works, walked through five
scenarios.
Does Your Entry Day Count as a Schengen Day? explains why border days count as full days under the official rule.
When Does Your Schengen Allowance Reset? describes why the 180-day window doesn't reset like a calendar.
Why this matters more than a confident-sounding answer
We've also written about why Schengen calculators give different results. A plausible number is not the same as a verified one, and a calculator that can't show you where its underlying rule comes from can't be checked against anything. That is also why an AI chatbot is not a substitute for this: it can generate a confident and plausible answer without providing any way to verify the result's accuracy for yourself.
If something looks off
If you ever run your dates and get a result that doesn't match what you find in the source we've cited, or a rule that seems out of date, cross-check it against that source, or against the official EU calculator. If they ever disagree, we want to know.