Staying over 3 months

Sophie, are your mother or father citizens of UK? If not it gets pretty difficult to get dual citizenship. I had a friend whos grandfather was Scottish, he was unable to get citizenship but was able to get a permanent residence card,, eventually, after much hassle, and he was in a long term relationship with a citizen and was completely finiacially independent . This was also more then a few years ago and he has commented that its even harder now.
Being American is no advantage or disadvantage, it means nothing really.

The previous reply is not accurate, but the way your question is posted (90 days in, 90 out), the answer is yes, you start a new 90 days in if you go back because you are starting a new 180 day period. (Leaving for a few days does NOT add the days back to your 90, since the 180 begins on the first entry. If you have used 30 days, you don't get 10 back by leaving for 10.)

Agree, Nicholas is way off. You do not get to add back days. It is very simple but sometimes difficult to understand. As you posed your question, you are correct. You can only be in the Schengen zone 90 days out of any 180 day period. So if you are in and out of the Schengen zone you will have several 180 period running and it can get complicated keeping track. What are your grounds for GB citizenship? If you can get it it solves your problem.

Nicholas, you do have it wrong in both posts. Each time you enter the Schengen zone you start a new 180 period, but any previous 180 period remains in effect. So people that enter Schengen multiple times have multiple 180 periods to keep track of. You show adding days for each time a person leaves; it doesn't work that way. If you enter Schengen for 30 days, then go to UK for 10 days, you still only have 60 days left, not 70. Sophie's OP scenario works in that she will be in Schengen for 90 days, then out for 90 to reset her clock. Enforcement may be haphazard per country/immigration official, but is getting much easier to track with electronic passports.

'If I spend 90 days within the Schengen zone then go to Ireland/UK for 90 days can I then re-enter the Schengen zone and have 90 more days?' - Yes, there is no doubt. Ensure you have entry and exit proof in documentation.

This is the problem with asking for immigration advice on a travel board. Everyone here has their interpretation of the law, but I doubt anyone here is an immigration specialist. For example, I was always under the impression that the 180 day period was rolling. For example, today the 180 day period is March 15 to September 10. Tomorrow, it is March 16 to September 11. If you had less than 90 days in that period in Schengen, you were in compliance. Is that the correct interpretation? I don't know. I think the point is that if you are going to be testing the limit then you need to get your advice from an official source.

Laura - you are basically right in that the 180 period is a rolling period and that if you do not exceed 90 days in the previous 180, you are in compliance. It's the easiest way to think of it. But the Schengen agreement also has specific language about "entry date", meaning that the 180 days starts at each date of entry into the Schengen area. So people that enter multiple times start a 180 period each time, but it doesn't reset the clock fresh, the previous 180 periods still apply. You are also right that getting into the nitty-gritty is not our expertise, but the OP's question was pretty direct. It was some of the answers that were incorrect and needed clarification.

I can concur with the earlier posts, you look OK, but pushing the limits of 90 days may not be wise, allow a few days buffer if possible. The 90 days also do not need to be in single blocks, you can come and go, just more confusing to track your days. It may also be worth noting that typically in the UK, as a US citizen you are good to stay for 6 months. Ireland is a non-Schengen country as well, but it is up to the border agent to a degree, if you have a return ticket in two weeks, you might get 30 days, or up to a max of 90 days. As with anything though, extended stays can prompt questions, they have the right to ask about where you will be staying, means of support, health insurance coverage, etc. if they suspect you may be longer term than just a "tourist" or engaging in activities for business.

Contact the U.S. State Department. The website contains information on Schengen and if you can call and double check, that is even better. They are at: www.state.gov Also see: travel.state.gov People on this website are very knowledgeable, but you should also check with the State Department and their staff. They would also know the "latest and greatest" on dual citizenship issues. Best wishes and happy travels.