"Take this past Tuesday, for instance. The weekend before, I learned there was an election because my girlfriend told me. Perhaps I should have known since they're at regular intervals, but I don't know what those intervals are."

General elections are held nationally the first Tuesday after the first Monday in November. This means they are limited to the dates of November 2-8 (but not November 1 if it falls on a Tuesday since there was no November Monday preceding it). Using this formula, you can note in advance when Election Day will take place every year.