A year on Eamon is the amount of time it takes for Great Eldur to return to the same position in the sky, thus marking one full revolution of the world. One year consists of just slightly more than 366 days, with the small remainder being made up through the addition of a leap day every 239 years.
On worlds like Earth or Golarion a year is nearly the same length as Eamon's. On other worlds it varies: Midkemia's year is just 200 days, while a year on Athas is 375 days.
