Resources
Longer explanations of the rules the calculators apply, written by the people who verify them.
The Schengen 90/180 rule, worked through on real dates
The 90 days do not reset on 1 January, and they do not reset when you leave. Here is what the rolling 180-day window actually does, with the arithmetic shown.
Does your arrival day count? Almost always, yes
The most common day-counting mistake, and the one that gets people refused at the border. Worked examples for Schengen, the UK and fixed-day permissions.
Six months is not 180 days
A six-month permission runs between 181 and 184 days depending on which months it covers. Here is when the difference bites, and by how much.
The two passport rules that get people turned away
For the Schengen area your passport must be valid three months beyond departure and issued within the previous ten years. Both are checked, and renewed passports fail the second one surprisingly often.
Days that do not count: European territories outside the Schengen area
Guadeloupe, Greenland, Svalbard and Aruba are not in the Schengen area, though France, Denmark, Norway and the Netherlands are. Those days are not Schengen days.
The UAE 180-day rule: how long you can be away before losing residency
A UAE residence visa is nullified automatically after more than 180 continuous days outside the country. No notice, no decision to appeal. Here is how to count it.
What overstaying actually costs, and why most sites will not tell you
Fines, bans and re-entry consequences vary by country and by officer discretion. Here is the one figure that is officially published, and why the widely repeated ten-day grace period is not stated anywhere official.