When different definitions were used

Artificial

1380 - 2007
1425 - 1977
1425 - 1991
1425 - 2006
1475 - 1868
1490 - 1833
1513 - 1734
1531 - 1821
1531 - 1794
1542 - 1999
1546 - 2001
1558 - 2007
1564 - 1962
1584 - 1970
1610 - 1999
1618 - 1957
1635 - 2000
1682 - 1860
1761 - 1999
1805 - 1991
1840 - 1977
1847 - 1977
1880 - 1995
1907 - 2001
1927 - 2003