If you have an Schengen visa, this means you may only spend up to 90 days in the Schengen area within any 180 day period. After this, you must leave the entire Schengen area. 

The 180 day period is a ‘rolling period’. This means it moves! Think of it like a 180 day shadow that you cast behind you (i.e. 180 days backwards) as you move forward in time. As you move forward, your shadow moves forward too, but it is always 180 days long.

Let’s take an example. Imagine the year is 2026. You spend 30 days in the Schengen countries in January, then you go outside the Schengen area, and then you come back to spend another 30 days in the Schengen area in April. At the end of April, you have spent 60 days of your 90 day allowance in the Schengen area (30 from January + 30 from April).

Now let’s imagine you leave the area again, and you come back in August to spend another 30 days in the area. At the end of August, you will still have only spent 60 days of your allowance in the area (30 days from April plus 30 days from August). Why? Because at the end of August, when you look at the 180 day ‘shadow’ behind you, it is still covering April, so April is included. But it has moved ‘forward’ on the calendar, and no longer covers January, so those 30 days are no longer included!

New rolling periods work in a similar way. Continuing with the previous example, let’s imagine you leave at the end of August 2026, and you come back again in May 2027. When you arrive in May, you will have your full 90 days available again, and your allowances will be reset. Why? Because when you look behind you, none of your previous trips fall within the 180 days before this new trip.