Age of each of these countries

USA: 250 years

Netherlands: 445 years

Sweden: 503 years

Spain: 547 years

Monaco: 729 years

Switzerland: 735 years

Thailand: 788 years

Mongolia: 820 years

Portugal: 883 years

Hungary: 1,026 years

Poland: 1,060 years

Denmark: 1,061 years

England: 1,099 years

Norway: 1,154 years

Russia: 1,164 years

France: 1,183 years

Morocco: 1,238 years

Bulgaria: 1,345 years

China: 2,246 years

Iran: 2,575 years

Japan: 2,685 years

Ethiopia: 3,000 years

Egypt: 5,125 years

For example, the United States marked its 250th anniversary in 2026, counting from the Declaration of Independence in 1776. Portugal is widely regarded as Europe's oldest nation-state, dating its independence to 1143, while Switzerland traces its origins to the Federal Charter of 1291.

Some entries, however, combine the age of civilizations with the age of modern states. Egypt's figure of 5,125 years refers to the unification of Ancient Egypt around 3100 BC, not the modern Arab Republic of Egypt established in the 20th century. Likewise, China's 2,246 years is based on the establishment of the Qin Dynasty in 221 BC, even though the modern People's Republic of China was founded in 1949.

Similarly, Iran's age of 2,575 years traces its statehood to the Achaemenid Empire founded by Cyrus the Great around 550 BC, while Japan's 2,685 years is derived from the traditional accession of the legendary Emperor Jimmu in 660 BC—a date rooted in tradition rather than universally accepted historical evidence.

The figure of 3,000 years for Ethiopia reflects the country's ancient civilization and historical continuity rather than the age of its present constitutional state. Other countries on the list, including France, England, Denmark, Hungary, Poland, and Morocco, also use historical milestones that differ from the formation of their modern governments.