Era
20th century
23
19th century
15
Precambrian
12
Quaternary
9
Cretaceous
7
Paleozoic
7
Tertiary
7
1945-
6
Permian
5
1896-1980
4
1945-1989
4
1981-1989
4
Cenozoic
4
-1400
3
1564-1616
3
1897-1962
3
18th century
3
1989-
3
Archaean
3
Mesozoic
3
Pleistocene
3
Pliocene
3
Revolution, 1775-1783
3
-1521
2
1743-1826
2
17th century
2
1882-1945
2
1884-1972
2
1945-1953
2
1948-1980
2
1949-1976
2
1975-1985
2
1985-1991
2
2001-2009
2
21st century
2
356 B.C.-323 B.C.
2
Carboniferous
2
Devonian
2
Early modern, 1500-1700
2
Holocene
2
Neogene
2
Pennsylvanian
2
To 1500
2
To 1863
2
To 500
2
-524
1
1333-1600
1
1469-1527
1
1556-1648
1
1568-1600
1
more ...