Adoption of the Gregorian calendar started to make the change from the Julian calendar and towards the Gregorian calendar in 1700, but it was decided to make the (then 11-day) adjustment gradually by excluding the leap days (29 February) from each of 11 successive leap years, 1700 to 1740. Meanwhile, the Swedish calendar would be out of step with both the Julian calendar and the Gregorian calendar for 40 years; also, the difference would not be constant but would change every four years. This system had potential for confusion when working out the dates of Swedish events in this 40-year period. To add to the
Middle-earth calendar more generally: The Elves also have a regular 365-day solar year called "coranar" meaning "sun-round" or more commonly "loa" meaning "growth". The Elven year, which began near the northward equinox, is divided into six seasons or 'months' which consist of four 54-day months and two 72-day months. Five or eight extra days outside the seasons make the length of the "loa" 365 or 368 days. Most years are 365 days, but every twelfth year is 368 days, resulting in an average year of 365.25 days with the additional suggestion that the 'Reckoning of Rivendell' made a further correction by omitting