Q: Context: The 26th Amendment (passed and ratified in 1971) set the voting age for federal and state elections at 18 years, but does not prevent states from establishing a lower voting age. Except for the express limitations provided for in Amendments XIV, XV, XIX and XXVI, voter qualifications for House and Senate elections are largely delegated to the States under Article I, Section 2 and Amendment XVII of the United States Constitution, which respectively state that "The House of Representatives shall be composed of Members chosen every second Year by the People of the several States, and the Electors in each State shall have the Qualifications requisite for Electors of the most numerous Branch of the State Legislature." and "The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years; and each Senator shall have one vote. The electors in each State shall have the qualifications requisite for electors of the most numerous branch of the State legislatures."

Question: when did the age to vote changed to 18? Let's give stream of consciousness first:
To answer this question, we should know that: The 26th Amendment (passed and ratified in 1971) set the voting age for federal and state elections at 18 years, but does not prevent states from establishing a lower voting age. Therefore, the final answer is 1971.