Schengen Clock — Rolling 90/180 Rule Tracker

Overview

The Schengen 90/180 rule is simple to state and brutal to apply: in any 180-day window (rolling backwards from today, or from any entry date), you may be present at most 90 days — visa-free or on a short-stay visa. The rolling part is what destroys people:

• Days don't "reset" when you leave for a weekend. The window slides every day.
• The 180-day window counts backwards from each day of presence, so a long stay from 7 months ago can still bite you today.
• Day of entry counts as day 1 of presence; day of exit also counts. Counting errors of 3–5 days are the most common cause of accidental overstays — which now mean entry bans (1+ years), not just a stern lecture at the border.

This skill turns stay history into certainty:

1. Stay registry — record entry/exit dates (+ country). Both dates count as presence days (that's the rule).
2. Rolling-window audit — for any date, compute presence in the trailing 180 days and remaining allowance.
3. Max-stay forecast — "if I enter on Oct 12, what is the longest I can stay?" — computed exactly, with the date allowance runs out.
4. Trip planner — "can I add Nov 1–Dec 12?" → verdict + adjusted allowance
   • which old stays are still "burning" inside the window.
5. Overstay traps — pattern-scan the registry for the classic mistakes.
6. Border letter — a dated itinerary + allowance statement to hand the border officer who asks "how long are you staying?"

All data in one local schengen.json. Travel history is nobody's cloud data.

When to Use

• You hold a non-EU passport with visa-free Schengen access (US, UK, UA, GE, AM, RS, MK, BA, MD, and ~50 more) and make multiple Europe trips per year
• You live partly in Europe on tourist stamps and need to know your exact runway
• You're planning trips and want to know: enter date X → max stay, or add trip Y → allowed?
• You over stayed once and need to understand your current standing before booking
• Border interview prep — printable allowance statement
• Don't use for: residence permits / national long-stay visas (D-visas) with separate rules, working-holiday schemes, or non-Schengen European microstates and Ireland/UK/Cyprus/Bulgaria/Romania (until they join — Romania and Bulgaria joined Schengen air/sea March 2024, land borders March 2025).

How It Works

1. stay add --entry 2026-05-10 --exit 2026-06-02 --country IT — record past/ future stays. Both dates count as presence days (day of entry AND day of exit both count — this is the official counting).
2. status --on 2026-10-01 — presence in the 180-day window ending that date, remaining allowance, burn-down of which stays are inside the window.
3. maxstay --entry 2026-10-12 — exact answer: if you enter Oct 12, the longest legal stay is N days, allowance exhausted on date D.
4. plan --entry 2026-11-01 --exit 2026-12-12 — verdict ALLOWED / TOO-LONG / EXACT-FIT with details; shows what the trip does to future allowance.
5. traps — pattern-scan the registry for the classic mistakes.
6. letter --entry 2026-10-12 --exit 2026-11-20 — border-interview one-pager.

Commands

# Record stays (past trips from passport stamps)
python3 scripts/schengen.py stay add --entry 2026-03-05 --exit 2026-03-18 --country FR
python3 scripts/schengen.py stay add --entry 2026-05-10 --exit 2026-06-02 --country IT   # 24 days
python3 scripts/schengen.py stay add --entry 2026-07-01 --exit 2026-08-30 --country ES   # 61 days
python3 scripts/sengen.py stay list                       # (typo-guarded anyway)

# Where do I stand today / on a date?
python3 scripts/schengen.py status                        # as of today
python3 scripts/schengen.py status --on 2026-10-01        # 43 used / 47 left in window

# If I enter on a date, how long can I stay?
python3 scripts/schengen.py maxstay --entry 2026-10-12
# → longest legal stay 47 days, must exit by 2026-11-27 (or earlier if rules change)

# Can I add this trip?
python3 scripts/schengen.py plan --entry 2026-11-01 --exit 2026-12-12
# → TOO-LONG: trip is 42 days, only 29 available in window ending 2026-12-12

# Classic-trap scan
python3 scripts/schengen.py traps

# Border letter
python3 scripts/schengen.py letter --entry 2026-10-12 --exit 2026-11-20

Storage: schengen.json in cwd (or --db). Fully offline.

The Counting Rules (as implemented)

Common Pitfalls

1. Counting the exit day as free. Exit day counts as presence. A "90-day" trip entered on day 1 must exit on day 90, not day 91.
2. Thinking a weekend out resets the clock. The window rolls; only days outside stop accumulating. A 2-day hop to London saves you exactly 2 days.
3. Back-to-back long stays. 90 days in, out for a week, 90 days back in — the second stay trips the cap almost immediately because the first stay is still inside the rolling window. traps flags this pattern.
4. Ignoring future-dated stays. The planner simulates the registry as if the trip happened; booked-but-not-taken trips count in projections.
5. Microstate confusion. San Marino, Monaco, Vatican have no border checks — time there is Schengen time. UK, Ireland, Cyprus are NOT Schengen.
6. Assuming the rule is 180 days per year. It is not. It's 90 per any rolling 180. A calendar-year mental model overestimates allowance.
7. Trusting airport "you're fine" over the math. Airline check of ten uses the same rolling math; border police always do. Trust status, not vibes.
8. Overstaying "just 3 days". Post-2017 enforcement: fines, removal, and entry bans that outlast the trip's value. A 3-day overstay can cost a 1-year ban.

Verification Checklist

• Presence math: entry and exit days both counted, inclusive
• Rolling window: status uses the 180 days ending on the query date
• maxstay searches day-by-day for the true maximum (not an approximation)
• plan simulates the trip added to the registry and re-audits every window
• traps detects: back-to-back long stays, thin-margin (<5 days) plans, stays ending inside the next 180 days, cumulative-year heavy usage
• letter output is dated, shows trips + allowance math, printable
• No network calls — registry never leaves the machine

References

• references/rule-explained.md — the 90/180 mechanics worked examples, border interview tactics, overstay consequences by severity, FAQ