United States senators, like many elected officials, are elected on Election Day, the Tuesday after the first Monday in November. Senate elections occur every two years. Senators are elected for terms of six years, so elections for each Senate seat only occur every six years.
Not all senate seats are up for election at the same time. Every two years, elections are held for approximately one-third of the 100 seats in the senate. As of July 2016, the next senatorial election is scheduled to take place in 2016. All other federal elected officials, and many state and local elected officials, are also elected on Election Day.