There’s another meaning to the question: How often are elections held in the US?
Federally, electons are held every two years, on the first Tuesday after the first Monday in November (i.e., on a Tuesday between November 2nd and November 8th). In each federal election, all the members of the House of Representives and on third of the Senators are up for election. In each second federal election, the President and Vice-President are elected.
At the state, county and local level, most elections are held on the first Tuesday after the first Monday in November. Every year, some elections are held somewhere, though more do happen in years when there are federal elections. Elections are held for legislators, judges, and members of the executive branch (from State Governors down) – and the picture varies from state to state, and often within states as well.
In addition, elections are often held in between these election days in some states. A Tuesday in May seems popular, perhaps because it’s half way between the November election days.
At the state, county and local level, it is very common to have referenda held at the same time as elections, on all sorts of topics, from amendments to state constitutions, to approving loans or sales taxes for local projects.
All levels also have primaries, conducted by government officials, with registered members of political parties voting to choose the parties’ candidates for election in the forthcoming elections. The best known of these are the primaries for candadates for President of the US, but they are held for all kinds of elective office, again varying from state to state. By their nature, these are held at varying times before the day for the real election.