Reckoning of Rivendell
The Reckoning of Rivendell or Calendar of Imladris is the only recorded Elvish calendar, as it was the only one known to the Hobbits. The Eldar measured time on two scales: First, long periods of time were reckoned in yéni, which corresponded to 144 solar years containing 8,766 enquië ("weeks") or 52,596 days. Second, the Elves acknowledged a single solar year, which was called a Coranar ("sun-round") or Loa ("growth"). A coranar contained six 'months' (more akin to seasons), rather than twelve, and they were not all of the same length, as shown below.
In addition to the six month-seasons, a coranar had additional days inserted into the calendar to bring the total to 365 days. The first day of the year was yestarë, which preceded Tuilë, and the last day of the year was mettarë, which followed Coirë. Between yávië and quellë were three enderi ("middle-days") which were doubled every twelve years as leap days.
The names of the six seasons and additional days of the coranar were:
|Quenya name||Sindarin name||English Translation||Length in Days|
|Enderi||Middle Days||3 or 6|
Other calendar adjustments to deal with inaccuracies are unknown. As stated above a yén would be over a day too long. There is an indication that the last year of every third yén had its enderi omitted, but any further methods of adjustment are unknown.