"Election Day in the United States
is the day set by law for the selection of public officials by popular ballot.
For federal offices, it occurs on the Tuesday following the first Monday of November
(so the earliest possible date is November 2 and the latest November 8).
Presidential elections are held every four years.
Elections to the House of Representatives and the Senate are held every two years.
Many state and local government offices are also elected on Election Day
as a matter of convenience and cost saving.
However, a handful of states hold elections for state offices during odd numbered, off years;
this varies according to state and local laws."
from Wikipedia
