Question: When did the voting age change from 21 to 18?
Disambiguated questions and answers: question: When did the debate begin to lower the voting age from 21 to 18?
By what date did some states change the voting age from 21 to 18?
In what year was a voting age over 18 outlawed?
answer: during WW II
1968
1971
Natural Questions answer: 1970s (from the Wikipedia article "Voting age")