Poland's constitution has been changed many times. The first officially recognized Poland was created in 1025. The Poland that we know today is actually the Third Republic, which was created on New Year's Eve in 1989. This makes Poland as old as 996 years and as young as 33 years.
Poland has a rich history dating back to the late tenth century when Christianity was adopted into what would eventually become the State of Poland under the Holy Roman Empire. Poland has been a dominant power in Europe throughout the years but eventually declined (as with most Eastern European countries) after two World Wars and the rise of the Soviet Union. The start of the initial Polish republic occurred after the end of the First World War, which saw Poland partitioned and turned into a non-monarchical country. Violence erupted across the country to counteract regime change, including the war between republican parties, the communist state, and imperialist sympathizers.
New problems came to light in 1939, as the start of the Second World War was marked by the Nazi-controlled German invasion of Poland. This was the first time that the modern "blitzkrieg" tactics were used, where heavily armored contingents would march directly into the capital and attempt to capture it before any meaningful resistance occurred from the rest of the military and surrounding countries. The capital of Warsaw was under Nazi control in just under two weeks. This caused the worst time in Polish history, as the country was split between Nazi and German control and the rest was given to the Soviet Union.
In 1989, Poland became the Republic we know today. Under a "Shock Therapy Program", the government quickly adopted a modern market economy and recovered much more quickly than its neighbors.
The country of Poland is 1058 years old, founded in the year 966.