Super Tuesday is one of the most important days in the US political calendar.

Fourteen states will hold primary elections across the country, with the results proving a strong indicator for the general election. And it's not just the number of states, but the number of delegates proving vital for those vying to be president.

As with the November election and numerous primaries leading up to it, Super Tuesday is - funnily enough - always held on a Tuesday. As with most things political, there is an archaic reason behind this seemingly random decision.

A law dating back to the mid-19th century is the source of why American elections are always on the second day of the week.

Approved in January 1845, the law states "that the electors of President and Vice President shall be appointed in each state on the Tuesday next after the first Monday in the month of November of the year in which they are to be appointed."

The reason for the decision was because of the generally religious and agrarian makeup of American society in the 1800s. Sundays were a day of rest, Wednesdays were commonly market day, and voting usually required a day of travel either side, so Tuesday was settled upon as the most suitable day.

Since this decision, general elections have always been held on the first Tuesday of November.