The Elves of J. R. R. Tolkien's creation are tall and beautiful, immortal and wise. They love music and mirth, song and stars. Through the long Ages they have battled the forces of Darkness to protect the beauty of the world. Their history is a rich tapestry, within which is woven strands of tragedy and of triumph, of hope and despair, of great deeds of courage and terrible betrayals of trust.
The Sundering of the Elves ~ The different tribes of Elves
The Calendar of Imladris ~ Days of the week, months, etc. and how they match up with our modern calendar
The House of Finwë ~ Family Tree of the High Kings of the Noldor
The House of Elwë ~ Family Tree of the Sindarin Nobles
The First House of the Edain ~ The House of Bëor
The Third House of the Edain ~ The House of Hador
The Line of Elros ~ Early Descendants in Númenor
The Kings and Queens of Númenor ~ The Line of Kings
Heirs of Elendil ~ The Kings of Arnor and Gondor
Chieftains of the Dúnedain ~ To Aragorn Elessar
The first group to journey to Aman was led by King Ingwë; they have lived in the Blessed Realm ever since, and became known as the Vanyar ("Fair Elves"). The second group was led by King Finwë. They too found their way to Aman, although many of them later returned to Middle-earth. They became known as the Noldor ("Wise Elves").
The third group was the Teleri ("Last-Comers"), whose name for themselves was the Lindar ("Singers"). This was the largest host, led by King Elwë. Some of them were daunted by the Misty Mountains and would not attempt the crossing; they remained on the eastern side along the Anduin and in the forests there that were later known as Mirkwood and Lothlórien. They were called the Nandor, and they took Lenwë as their King. Some of the Nandor were later led by Lenwë's son Denethor into Ossiriand, the eastern part of Beleriand, and were called the Laiquendi or Laegrim "Green-Elves".
In eastern Beleriand Elwë went out alone and was drawn by the vision of Melian, a Maia, and fell under her enchantment. Many of the Teleri remained there searching long for their King, for they would not leave without him, and they called themselves Eglathrim ("Forsaken Ones"). After Elwë returned to them and founded Doriath, they called themselves Iathrim ("Fence-folk").
Others of the Teleri continued to the western shores of Beleriand and dwelled there a long time, but eventually they, too were sundered. Those who departed for Aman became known as the Falmari, the Sea Elves, and made their home at last in Alqualondë; those who remained on the shores of Beleriand became known as the Falathrim, the Shore Elves. Círdan was their Lord, although they still held Elwë as their King.
Spring ~ ethuil (Q. tuilë)
Summer ~ laer (Q. lairë)
Autumn ~ iavas (Q. yávië)
Fading ~ firith or narbeleth (Q. quellë or lassë-lanta)
Winter ~ rhîw (Q. hrívë)
Stirring ~ echuir (Q. coirë)
Summer and winter both lasted for 72 days; the other seasons were each 54 days long.
In every idhrinn there were five additional days that were not considered a part of any season and were celebrated as holidays. Between Autumn and Fading were three middle-days called enedhoer (translated from the attested Quenya name enderi). They were named Ethuilor "Spring-day", Inenedh "Year-Middle" (Mid-Year's Day according to the calendar of the Elves), and Iavasor "Harvest-day" (translated from the attested Quenya names: tuilérë, loëndë, and yáviérë). The first day of the year was Maninor "First Year-day" (translated from Quenya yestarë), and the last day of the year was Penninor "Year-full Day" (Q. mettarë).
This produced an idhrinn of 365 days, but to keep a deficit of minutes from building up over time, every 12th idhrinn had double-middle-days (so six instead of three, the Elvish equivalent of a leap-year) to get an în of 144 idhrinn. Then every third în had to be shortened by three days - eliminating the doubled middle-days one time - to adjust the calendar yet again!
January ~ Narwain "New sun" (Q. Narvinyë)
February ~ Nínui "Watery" (Q. Nénimë)
March ~ Gwaeron "Windy" (Q. Súlimë)
April ~ Gwirith (Q. Víressë)
May ~ Lothron "Flowering" (Q. Lótessë)
June ~ Nórui "Fiery, sunny" (Q. Nárië)
July ~ Cerveth (Q. Cermië)
August ~ Úrui "hot" (Q. Úrimë)
September ~ Ivanneth "Fruit-giving" (Q. Yavannië)
October ~ Narbeleth "Sun waning" (Q. Narquelië)
November ~ Hithui "Misty, foggy" (Q. Hísimë)
December ~ Girithron "Shuddering" (Q. Ringarë)
Star-day ~ Orgilion (Q. Elenya)
Sun-day ~ Oranor (Q. Anarya)
Moon-day ~ Orithil (Q. Isilya)
Two-Trees-day ~ Orgaladhad (Q. Aldúya)
Heaven-day ~ Ormenel (Q. Menelya)
Valar/Powers-day ~ Orbelain or Orodyn (Q. Valanya or Tárion)
The last one was the most important day of the week, called a High Day.
The Númenóreans added a seventh day, Sea-day (Oraearon, Q. Eärenya) before Valar-day, and changed Tree-day to singular (Orgaladh, Q. Aldëa), to honor only Nimloth the White Tree, rather than the Two Trees of Valinor, Telperion and Laurelin.
I have seen several attempts to align our modern-day calendar with the Calendar of Imladris. I cannot vouch for their accuracy, but it's nice to have something. The Encyclopedia Of Arda offers an interactive calendar that lets you type in any date on our Calendar and have it "translated" into the Calendar of Imladris, Shire Reckoning, etc. By their reckoning...
March 28th = Maninor, the first day of the year (Q. Yestárë)
March 29th = first day of Ethuil "Spring" (54 days long)
May 22nd = first day of Laer "Summer" (72 days long)
August 2nd = first day of Iavas "Autumn, Harvest" (54 days)
September 25, 26, 27 = Enedhoer "Middle-Days": Ethuilor, Inenedh, Iavasor
September 28th = first day of Firith "Fading" (54 days long)
November 21st = first day of Rhîw "Winter" (72 days long)
February 1st = first day of Echuir "Stirring" (54 days long)
March 27th = Penninor "Last Year-day"
Reference to a celebration in Gondolin called The Gates of Summer suggests that the first day of Laer might be recognized in Imladris as a special day; one could thus expect the first day of Rhîw to be the Gates of Winter. These might have been named in Sindarin Ennyn Laer and Ennyn Rhîw.