I was wondering if there's a historical reason for the four year presidential term length in the US. Why not three years or five years? Is it completely arbitrary? Was it based on the term lengths of previous democracies or other institutions? If so, why do they use that particular term length?
I do not know of any background around the rest of the world, but... "[The President] shall hold his Office during the Term of four Years...."
ARTICLE II, SECTION 1, CLAUSE 1
The four year term limit set by the Constitution differs from that of the limit set by Benjamin Franklin's Constitution for Pennsylvania, which set an executive group of twelve men elected to three year terms. In the Articles of Confederation, the fifth Article stated that "no person shall be capable of being a delegate [to the continental congress] for more than three years in any term of six years". So they all generally leaned towards three years instead of four. I have never read about an exact reason why it was set at four, but it was. But really, they were hitting around the ballpark for area of 3 to 4 years for a term anyway, so you could view it as an established precedent from some of the already written state's constitutions.