The Schengen 90/180 rule, explained

If you visit the Schengen area without a residence permit or long-stay visa, your stays are capped at 90 days within any rolling 180-day window. The window is the part most people get wrong: it is not a calendar period and it never “resets” on entry. On every single day, the question is how many of the preceding 180 days you were present.

How the window behaves

Because the window rolls, days do not expire on a fixed date — each counted day drops out of the window exactly 180 days after it occurred. Two consequences follow.

• A long absence does not bank you extra days. The most you can ever have available is 90 within the current window.
• Leaving does not stop the clock so much as start draining it. Days you used continue to count against you until they age out of the window, one by one.

This is why a compliant pattern of repeated visits can still drift toward the limit: what matters is the density of presence inside the trailing window, not the length of any single trip.

Which days count

Entry and exit days both count in full, however short — landing at 23:40 uses a day. Arriving and leaving on the same day uses one day. Staying airside in transit, without crossing border control, uses none. All Schengen states are counted together as one territory: three weeks split between Spain, Italy, and Germany is counted the same as three weeks in one of them.

What Residay computes and what it asks

From your trips, the app derives days used, days remaining, the projected date you would breach the limit if you stayed, and the next date a day frees up. One fact it cannot observe: whether you hold a residence permit or national long-stay visa for a Schengen state. It asks, because days spent in the state that issued your permit or D-visa do not count toward the limit.

Planning notes

• The limit binds per person, not per passport stamp — inconsistent stamps do not change the legal position, but they make your own evidence more valuable.
• Overstay consequences are set by each member state and can include entry bans; the margin for error is small enough that counting by hand is a poor strategy.
• Nationals of some countries have bilateral visa-waiver arrangements with individual member states that interact with the limit in unusual ways; verify before relying on one.