J.R.R. Tolkien>
The Lord of the Rings
The Reckoning of Rivendell was the calendar system used by the Elves of Imladris and is the only recorded calendar of the Eldar. It was made up of sixth months, and was arranged so that it reflected the Elven preference of counting in sixes and twelves. The year was called a loa, but they also divided time into spans of 144 loa(s), which were called Yéni. Yéni was the main unit of time for the Elves because of their indeterminate lifespans.
The leap year system of the Reckoning was considerably different from those of the Edain because instead of adding a day every four years, it added three days every twelve (Elves like Twelves). During leap years, the Enderi ('Middle-days', a constant from year to year in the Reckoning) were increased from three to six days.
It consisted of:
- Yestarë - New Year's day. Equivalent to our April 7th
- Tuilë - 54 days.
- Lairë - 72 days.
- Yávië - 54 days.
- Enderi - 3 days, 6 in a leap year.
- Quellë - 54 days.
- Hrívë - 72 days.
- Coirë - 54 days.
- Mettarë - The last day, one day.