The following is written in an unpracticed, childish hand upon a well-worn sheet of parchment, which is carefully folded and tucked within the back cover of Legelion's Narn Hên i-Laegrim. It is obviously an early exercise in writing Sindarin in the Angerthas Daeron, but it appears to have been referred to very often since.
Thus is the reckoning of a sun-round year as told to me -- Methlegel Feveren son of Gellin Dringor, son of Echeleb Túbeng, who is called Legelion -- by Teithoron Tegilbor, scribe to Thranduil Elvenking of the Woodland Realm in Rhovanion.
It was brought hither to Mirkwood in the fift sev 750th year of the Sun of the Second Age of Middle-earth by King Oropher of Doriath, for the wisdom of the Silvan Elves, his loyal subjects. (Save for Echeleb... haha!)
- - Now is the Third Age of Middle-earth since the rising of the Sun.
- - The First Age lasted for 590 years until the War of Wrath and the downfall of Morgoth Bauglir, the Dark Tyrant.
- - The Second Age lasted for 3441 years until the War of the Last Alliance and the downfall of Sauron Gorthaur, the Enemy.
* * *
There are six seasons in a year.
They are:
Iestor[1] which is the first day of the year
Ethuil which has four and fifty days
Laer which has two and seventy days
Iavas which has four and fifty days
Enedhoer[1] which are three days amidmost, but become six days every twelve years
(Alas! This is a riddle beyond my skill, but Teithoron says the reasoning thereof is uncommonly complex!)Firith which has four and fifty days, and is also called Narbeleth
Rhîw which has two and seventy days
Echuir which has four and fifty days
Methor[1] which is the last day of the year
- Thus today is the 35th day of Firith in the 2977th year of the Sun of the Third Age of Middle-earth
- I was begotten on the 51st day of Iavas in the 2964th year of the Sun of the Third Age of Middle-earth
- And I was born on the 53rd day of Iavas in the 2965th year of the Sun of the Third Age of Middle-earth and I have but lately turned twelve years of age.[2]
Teithoron says practice makes perfect! (And he says this often!)
* * *
There are six days in a week.[3]
They are:
Orgilion is the first day and it is dedicated to the Stars of Elbereth
Oranor is the second day and it is dedicated to the Sun
Orithil is the third day and it is dedicated to the Moon
Orgaladhad is the fourth day and it is dedicated to the Two Trees of Valinor
Ormenel is the fifth day and it is dedicated to the Heavens wherein dwell the stars
Orbelain is the sixth day and it is dedicated to the Valar, the Powers of Arda (it is also sometimes named Rodyn)
But wherefore the swift days are named, I know not!
* * *
A 'year' can be written as a coranor or a lóran. (O! I like this one!)
And there are 144 years of the Sun in a Long Year (which is named a yén in Quenya.)
Therefore this is Yén 49, Loa 96 or the 7008th sun-year in the reckoning of the Elves[4]... yet Teithiron deems it best that I reckon in the Years of Men!
But the elven-year begins in Spring and the mannish year in mid-winter, so how does this tally? I do not follow!
Rhaich! Reckoning is highly bewildering... I deem numbers are my unfriends!
* * *
Elo! Teithoron says my pen-form[5] is improving! But alas! he says also that the skilled scribe records what is spoken only, and I must therefore refrain from affixing my own thought. (Although 
I deem it fair writing practise!)
[1] "Tolkien did not give the Sindarin words for these holidays in Appendix D. These translations from the Quenya were provided by Sindarin expert /u/Elaran in the /r/sindarin subreddit."
- Shire Reckoning: A visualization of the calendars described in J.R.R. Tolkien's The Lord of the Rings Appendix D[2] "... a year passes between the begetting and the birth of an elf-child, so that the days of both are the same or nearly so, and it is the day of begetting that is remembered year by year."
- Morgoth's Ring, 'The Laws and Customs Among the Eldar'[3] "For ritual rather than practical purposes the Eldar observed a week or enquië of six days."
- The Lord of the Rings, Appendix D, 'The Calendars'[4] Calculated (probably wrongly!) using Shire Reckoning Calendar Simulations.
[5] "The Certar were devised and mostly used only for scratched or incised inscriptions. [...] Dwarves made use of such scripts as were current and many wrote the Fëanorian letters skilfully; but for their own tongue they adhered to the Cirth, and developed written pen-forms* from them."
- The Lord of the Rings, 'Appendix E: Writing'* It is my guess that the Iathrim would have too.
It is assumed that the Silvan Elves of Mirkwood had no need for a formal calendar, but the Sindar brought with them from Doriath the same elven calendar that was later used in Imladris.
