TL;DR — Key Takeaways
- →Days before 1 January count in the old tax year. Days from 1 January count in the new one.
- →Schengen 90/180 does not reset on 1 January. It is a rolling 180-day window.
- →A year-crossover alert is useful so the December portion is not forgotten at filing time.
- →The split is a planning count, not a residence determination.
Short answer
Split the trip on 31 December. Nights in the old year stay in that year's country total. Nights from 1 January go to the next year. Do not assign the whole booking to the year you booked it.
Two clocks on the same dates
- Tax-year day count — usually a calendar year, sometimes a different fiscal year. The boundary is the country's tax year, not your flight confirmation.
- Schengen 90/180 — keeps rolling. A day in January can still sit inside a window that started in July.
Domicyle Residency Tracker stores entry and exit dates so a trip that crosses the year is not one blob. Alerts can flag a trip that crosses into the next tax year.
Educational planning only — not tax advice.