Era
20th century
33
19th century
15
Quaternary
14
Precambrian
12
Cretaceous
10
Paleozoic
10
1945-
9
Permian
8
Tertiary
8
Cenozoic
7
Mesozoic
7
Carboniferous
6
1945-1989
5
1965-
5
Pennsylvanian
5
1564-1616
4
1897-1962
4
1981-1989
4
Archaean
4
-1400
3
Jurassic
3
Pleistocene
3
Revolution, 1775-1783
3
Silurian
3
17th century
2
1809-1865
2
1813-1883
2
1856-1924
2
1882-1945
2
1884-1972
2
1896-1980
2
1899-1961
2
18th century
2
1902-1968
2
1933-1945
2
1945-1953
2
1948-1980
2
1949-
2
1949-1976
2
1951-
2
1960-1980
2
1975-1985
2
1989-
2
2001-2009
2
21st century
2
356 B.C.-323 B.C.
2
Colonial period, ca. 1600-1775
2
Devonian
2
Early modern, 1500-1700
2
Neogene
2
more ...