Era
20th century
89
19th century
39
1945-
33
18th century
21
Revolution, 1775-1783
16
16th century
15
17th century
14
1564-1616
11
Middle Ages, 600-1500
11
1897-1962
10
Middle English, 1100-1500
10
1989-
9
1960-
8
1882-1941
7
1896-1980
7
1900-1999
7
1933-1945
7
1981-
7
To 1500
7
1945-1989
6
1948-
6
1979-
6
Colonial period, ca. 1600-1775
6
Early modern and Elizabethan, 1500-1600
6
Medieval, 500-1500
6
1066-1485
5
1775-1865
5
1950-
5
1975-1985
5
Early modern, 1500-1700
5
Old English, ca. 450-1100
5
Renaissance, 1450-1600
5
1982-
4
1985-1995
4
Precambrian
4
Revolution, 1789-1799
4
To 1803
4
1644-1912
3
1743-1826
3
1775-1783
3
1788-1824
3
1818-1883
3
1868-
3
1879-1955
3
1883-1946
3
1918-1945
3
1945-1971
3
1947-
3
1976-
3
1980-
3
more ...