For the most part they are held every two years in November, in even numbered years. Next year is the so-called midterms, which will elect among other things the entire House of Representatives and 1/3 of the Senate. Every 4 years (2024, 2028, etc.) is the presidential election. For the Senate and Representatives, in practice, most of the incumbents get re-elected without much difficulty, but some seats will be in play.

In odd numbered years like 2025, there are a few elections like Mamdani’s and a couple of stage governorships, but there are far fewer seats in play than in even numbered years.

There are also occasionally special elections that can be anytime, i.e. in months other than November. Also, there are primary elections (not deciding who gets an office, but rather, who gets to be a party’s nominee for that office) that are held some months before the November (“general”) election.

Finally there are various kinds of local elections that are not entirely synchronized with the ones for federal offices.