Here is a timeline containing useful/relevant events from the recent past. I'll update it with suggestions and as the RP/Players reveal other past events.
4E 0A new era begins after the Oblivion Crisis comes to an end.
4E 22The Thalmor came into power of Summerset Isle. Summerset Isle is renamed to Alinor, but is still referred to as Summerset Isle outside the Third Aldmeri Dominion.
4E 29The government of Valenwood is overthrown by the Thalmor sympathizers. The Bosmeri, allied with the Empire, were unprepared. Valenwood becomes a Thalmor territory.
4E 115Coup against the Elsweyr Confederacy takes place. Elsweyr is divided into the kingdoms of Anequina and Pelletine, as extensions of the Aldmeri Dominion.
4E 171The Ambassador of the Aldmeri Dominion orders the Empire to step down from power. The Empire resists, and the Great War between The Empire and the Aldmeri Dominion begins.
Aldmeri forces led by Lord Naarifin invade Hammerfell and Cyrodiil. The city of Leyawiin falls, and the city of Bravil is besieged.
A 2nd Aldmeri force, led by Lady Arannelya, cross western Cyrodiil and invade Hammerfell. The Redguards in Hammerfell, divided by civil war and disorganized, put up little resistance. The southern coastline falls to the Aldmeri forces as the Imperial Legions in Hammerfell retreat North into the Alik'r Desert.
4E 172Aldmeri forces advance into Cyrodiil to capture the Imperial City.
The cities of Bravil and Anvil in Cyrodiil both fall to Aldmeri forces. Naval battles ensues in Lake Rumare surrounding Imperial City and along the Niben River leading to the Rumare.
4E 174Cyrodiil: The Thalmor leadership decides to focus their forces in the Cyrodiil campaign and the Imperial City falls to the Aldmeri forces.
4E 175The Battle of the Red Ring takes place as the Empire embarks on a campaign to retake Imperial City, which fell to the Aldmeri Dominion the previous year. The battle was an Imperial victory, but not without heavy losses.
Exhausted from war, the Empire negotiates a peace treaty and signs the White-Gold Concordat with the Aldmeri Dominion, thus ending the war. The terms of the agreements are the surrender of the remaining territory still occupied by Aldmeri Force, and the banning of the worship of Talos. Thus, the Great War ends.
As a result of the White-Gold Concordat, relationship between the Imperials of Cyrodiil and the Redguard of Hammerfell deteriorated. Although allies during the war, the Empire is forced to renounce Hammerfell as an Imperial province.
All the Elder Scrolls housed in the libraries of White-Gold Tower vanish, and are scattered across Tamriel by unknown means.
4E 180As a follow-up to the White-Gold Concordat, the Second Treaty of Stros M'kai is signed, which decrees that Aldmeri occupation forces are to withdraw from Hammerfell
4E 201Civil War begins in Skyrim.
Alduin returns on the 17th of Last Seed, first attacking the town of Helgen.
Alduin is slain by the Dragonborn during the Battle of the Tongues.
4E 202Civil War ends, eventually resulting in an Empire victory. The Empire looses both Tullius and Elisif the Fair in the war.
The College of Winterhold discovers the Eye of Magnus, which nearly destroys the city of Winterhold.
Emperor Titus Mede II is assassinated.
4E 203Jarl Balgruuf the Greater is selected by the Jarls of Skyrim to become the next High King.
Janos Cornilo becomes the next Emperor, but is assassinated shortly after.
Politics in the Imperial City become increasingly hostile and no one is able to get the throne.
4E 214High King Balgruuf is murdered by his youngest son, Nelkir. Nelkir's older brother, Frothar Steel-Fist then captures and executes him.
Frothar becomes the new High King of Skyrim and is considered by many to be a good Nord like his father.
4E 217Mages claim that a large door to Oblivion was opened Temporarily in the South West of Morrowind.
The Vigilants of Stendarr claim that there has been an increase in Daedra cults.
4E 220Reports of body snatching seem to pop-up all over Tamriel, but are repeatedly denied by officials.
4E 221Taking advantage of the weakened state of the Empire, the Aldmeri Dominion breaks the peace treaty and reignites the Great War.
Whilst the Dominion gathers its forces in Bravil, Legate Fasendil infiltrates Leyawin with a large unit of Imperial Altmer and takes back the city, releasing it from 50 years of occupation.
A large Dominion fleet is ambushed and destroyed by Imperial forces stationed at Leyawin.
A surprise rebellion in Elsywer, which is backed by Black Marsh, draws away the Dominions resources and weakens their invasion.
Dominion forces fail in an effort to retake Leyawin, but deal heavy damage to Imperial forces.
Due to heavy losses and a disruption in supply lines, the Dominion is forced to withdraw from Blackwood and a large part of the Nibenay Valley (with the exception of Bravil).
4E 222The Aldmeri Dominion takes Kvatch.
The Aldmeri lays siege to Skingrad but is beaten and pushed back.
Dominion forces regrouping in the Colovian Highlands are attack by a large force from Hammerfell, who come to the aid of the Empire.
Intense fighting engulfs the Gold Coast and the West Wield, as both sides throw all they have at each other.
4E 223
The Empire seems to be faring much worse than the Dominion, but neither side gains any significant ground.
Black Marsh claims to be a neutral party but are accused by the Dominion of supporting Khajit rebels and providing reinforcements and provisions to the Imperial forces at Leyawiin.
4E 224Current time - The Dominion has laid siege to Leyawiin in an attempt to reclaim it.