Era
20th century
48
1900-1999
30
19th century
19
18th century
18
Civil War, 1861-1865
12
1945-
11
1939-1945
10
Colonial period, ca. 1600-1775
9
Revolution, 1775-1783
8
1945-1991
6
1951-
6
Revolution, 1917-1921
6
1800-1837
5
1809-1865
5
1869-1934
5
1900-1945
5
1979-
5
20e siècle
5
Since 1979
5
1917-1921
4
1918-1945
4
1945-1980
4
1975-
4
Since 1945
4
1760-1789
3
1860-1918
3
1898-1946
3
1933-1945
3
1945-1989
3
Since 1918
3
1699-1777
2
1783-1850
2
1783-1865
2
17th century
2
1881-1945
2
1892-1984
2
1917 - 1921
2
1917-1945
2
1918-
2
1918-1938
2
1931-1939
2
1934-
2
1939-1975
2
1944-1989 (Polska Ludowa)
2
1945-1992
2
1953-1985
2
1955-
2
1973-
2
1976
2
1979-1992
2
more ...