Every country requires a valid passport for entry, but a lesser-known requirement for many countries is that a U.S. passport must be valid for a fixed number of months from the traveler's date of entry. Some countries tweak the requirement slightly, and each country makes its own rules which sometimes change, so it is wise to know beforehand. Renew a passport early to avoid any unforeseen difficulties.

U.S. Passport Expiration

On U.S. passports, the date of issue and date of expiration are found on the inside front cover next to the passport holder's photo. The standard validity is 10 years. Some countries deny entry to anyone holding a passport that expires in less than three months or six months. This restriction may apply to the date of entry or the intended date of departure. A good source of up-to-date information about international entry requirements is the U.S. Department of State's website where a drop-down option provides country-by-country details, visas, vaccinations, travel alerts and warnings. Travelers may also consult the embassy or consulate websites of countries they plan to visit. Given any question or approaching cutoff date, prompt passport renewal is the best strategy.

Traveling to Europe

The Schengen Agreement includes 26 European countries that require a passport be valid for at least three months beyond the intended date of departure. These countries are Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden and Switzerland. A visitor spending three months in the Schengen area during any six-month period must wait another three months, after departing before applying to enter the Schengen area again without a visa. Otherwise, contact the embassy of the country where the majority of time during the visit will be spent to apply for a visa.

Note that the United Kingdom and Republic of Ireland do not adhere to the Schengen rules. requirement; a valid passport is accepted with no minimum validity enforced. Policies among the other European nations outside the Schengen Agreement vary; for example, in Albania, Belarus and Croatia, a passport must be valid for three months beyond a scheduled departure date.

Visiting Asia or India

A six-month validity requirement for U.S. passport holders is common on the Asian continent, with a few notable provisions or additional requirements. In Hong Kong and Macau, a passport must be valid one month past the intended date of departure. Russia and India require at least six months' validity plus two blank passport pages for official stamps and a tourist visa, with India requiring that passport validity start from the date of visa application rather than date of travel.

Trips to the Middle East

Some Middle Eastern nations require a blank page for an entry stamp and possibly a tourist visa. Most have a six-month validity requirement as follows: Bahrain, Egypt, Iran, Iraq, Israel, Jordan, Kuwait, Saudi Arabia, United Arab Emirates, West Bank/Gaza Strip and Yemen.

Travel to Africa

Most African nations apply the six-month validity rule. These are: Algeria, Angola, Botswana, Burundi, Cameroon, Central African Republic, Chad, Congo, Cote d’Ivoire, Djibouti, Equatorial Guinea, Eritrea, Ethiopia, Gabon, Kenya, Madagascar, Malawi, Mauritania, Mozambique, Namibia, Rwanda, São Tomé and Príncipe, Somalia, South Sudan, Sudan, Tanzania, Uganda and Zambia.

Within The Americas and the Caribbean

Canada and Mexico do not enforce the six-month rule for U.S. passport holders, although the one blank page requirement does apply. Caribbean and Central American nations that enforce the six-month validity rule are Antigua and Barbuda, Grenada, Guadeloupe, Haiti, Honduras, Martinique, St. Barthelemy, St. Kitts, St. Lucia, Trinidad and Tobago, and Panama (where the passport must be valid three months beyond arrival). In Latin America, the six-month rule countries are: Bolivia, Ecuador (including the Galapagos Islands), Guyana, Suriname, and Venezuela.

Going to the South Pacific

In Australasia and the South Pacific, travelers need six months' minimum validity on a U.S. passport for travel to French Polynesia, Kiribati, Marshall Islands, Micronesia, New Zealand (where the passport must be valid one month beyond planned departure), Palau, Papua New Guinea, Tonga, Tuvalu and Vanuatu. To enter Australia, a passport valid at time of entry is valid but must be accompanied by a visa or Electronic Travel Authority registration.

Disclosure Leaf Group is a USA TODAY content partner providing general travel information. Its content is produced independently of USA TODAY.

About the Author Based in San Francisco, Laurie Jo Miller Farr is career-long destination and hotel marketing specialist. She contributes to CBS Travel, Where, Frommers, Foodie Travel USA and We Blog the World. She is editor of The Travel Vertical, a weekly newsletter for digital travel marketers. A former tourism director for NYC, Laurie Jo is a dual UK/US citizen who covered the 2012 London Olympics for "Best of Britain" and received the 2013 Yahoo Contributor of the Year Award.