U.S. traveler in Europe for six months

It's not the European Union- it's the Schengen agreement. The UK does not participate in the Schengen agreement, neither do some other countries- so do some research and see if you can plan things around that. I'd also look into getting a visa though your first entry country. See what the requirements are, then decicde if you can meet them.

There is a lot of information on this board, and others, about this question. Also, look up what countries are included in the Schengen agreement and see if you can work with that. UK is certainly not part of it and could be a good option for some of the time - it is however, extremely expensive. Not all EU countries are part of Schengen - e.g. Bulgaria is not. Many people suggest getting a long term visa for the European country you plan to spend the most time in, which is doable is probably impractical for an extended holiday. We have done this for Spain but it was to live there.

If you do a back search on this site you will find a lot of discussions. This is a tight requirement than cannot be avoided. Assuming you do not get an extended stay for another country, this a summary of what you pattern might be: Jan 1 - First entry into Schengen zone. A 90 day and 180 day clocks begins. Mar 1 - Go to Great Britain - the 90 day clock stops with 59 days used up, 180 day clock continues to run. Apr 1 - Go to Paris - 90 day clock resumes at 59 days 180 day clock continues. You can stay in Paris till May 1. Your are done. You need to get out of the Schengen zone and stay out till after June 29. Now this is where it gets tricky in the application. Some say you could go back on July 1 and it starts over. Some others says, that a second 180 clock started when you returned to Paris on Apr 1. And it double counts your days. Your 31 days in Paris are a part of the original 180 and also counts as 31 days against the new 180 day period that started on April 1. I don't know. However, since passports are not always stamped at entry/exit points, you need to keep a little documentation, hotel receipts, etc. when you are out of the Schengen zone so that you can show that you were gone. Good luck. PS - just for terminology sake - a United States tourist visa is for visitors coming to the US. Visa are issued by the country that you are traveling to as permission to enter. Technically speaking the Schengen visa for 90 days is automatic for citizens of certain counties including the US but it is still a visa. PPS - A father reported last year that his daughter over stayed one day and was fined 500E on the spot. Others have reported no problems overstaying a few days. Who knows ??

In Frank's scenario, another 180 clock starts when you re-enter Schengen for Paris. But the old 180 clock also keeps ticking. The best way to think of the 90 in 180 rule is to consider the 180 "clock" as always running, and if anytime in the past 180 days, you exceeded 90 days total in Schengen, then you are in violation. Given that you will need to account for 90 days of your trip outside Schengen, you may best look into an extended visa. Unless you are planning to spend considerable time in the UK and eastern Europe.

@Frank: EU has been deploying this thing called Frontex. It is actually a wider program but for reasons concerned here it means that more and more points-of-entry in EU/EEA (Schengen or not) are being electronically integrated. On top of that, "chip" passports don't need to be stamped, they are automatically read and information from them stored in computers of Frontex. This means, for instance, that an immigration agent in København and see that another immigration agent in Frankfurt registered and entry at the airport on date x. The main purpose of the system is for information exchange on deportations, arrest warrants, terrorism watch etc. But it also serves to integrate customs throughout Schengen. With or without stamped passports. It is very risky to assume lack of stamp = no one registered your entry. There are many ways to do that, such as airline passenger records exchanged with Frontex etc.

The Department of State for the country you are a resident of can accurately answer your questions. If you are a US citizen, see this link, http://travel.state.gov/travel/cis_pa_tw/cis/cis_4361.html

Many thanks to you all. The information will get me started on my quest and next adventure.