If you assume (and you know what they say about assuming!), that your passport expires on a certain date and it will be valid right up until that date, you could get an unpleasant surprise. When it comes to passports, some countries require that your U.S. passport be valid not only for the duration of your visit, but also for three to six months after your entry or return from their country.

Not only should you ensure that there is enough time remaining for you to complete your trip, but also if it is even close to expiring there may be problems. The length of time varies from country to country so check well before you leave on travel.

If it isn’t confusing enough already, some countries count their expiration windows from date of entry into their country, others from scheduled departure, so be sure to check for the various countries you may be traveling in.

What do you do if your passport will expire in less than six months:

1. Contact the host country’s embassy or consulate to see if you can get a special visa for travel within the expiration period.

2. Renew your passport. You should allow six weeks for renewal, but it often takes less particularly if you apply during the off-season months of September or December, when relatively few travelers apply for passports. You can also apply for an expedited renewal for an additional fee to get your passport renewed in about two weeks.

For more information about special passport expiration rules, check the U. S. Department of State’s listing of foreign entry requirements. Other good sources of information are airlines, travel agents, host country’s embassy or consulate, or the National Passport Information Center, (877) 487-2778, travel.state.gov/passport.