This year (2016), it is the same day as the Presidential elections, Nov.8th.
They have to be 30 by election day to run.
Senators are elected into power the same way the president is. When the Senator in your area is up for re-election there will be one held on the same day as the presidential election.
The general election day for the President, U.S. Senators, and members of the U.S. House of Representatives is the Tuesday right after the first Monday in November (i.e. the first Tuesday after November 1st).
Secret ballots
The 17th Amendment changed the election of Senators from state legislators. The 17th Amendment elects Senators by popular vote of the constituents.
U.S. Senators are elected for a six-year term. One third of the Senators are up for election every two years.
Direct election of senators to Congress occurred because of the 17th constitutional amendment.
Direct election of senators
NO
no
The seventeenth amendment addressed the issue and process of the election of the US senators.
Richard Durbin (D) and Tammy Duckworth (D) are the U.S. Senators representing Illinois. Durbin's next election will be in 2020. Duckworth's next election will be in 2022.