Azeroth Timeline

If a date provided is estimated, it will be italicized.
Unknown Year: C'thalos enacts Sheu'thalon (The Great Creation)
1,000,000,000 L.D: Darak'thenon is condemned to the Realm of Atrimi.
11,000,000 L.D: Cataclysar, Kerah, Solarion, and Terralos create the Elemental Lords under C'thalos' orders, these Lords becoming the first beings on Azeroth.
10,500,000 L.D: The Elementals are first created.
8,000,000 L.D: Solaht'c embeds the manifestation of his sin into Azeroth in an attempt to destroy the planet. His sin manifests itself as the Old Gods.
7,000,000 L.D: The Old Gods create the first N'raqi.
5,000,000 L.D: C'thun creates the first Aqir.
4,000,000 L.D: The First Generation Titan-Forged and the Keepers are first created.
3,000,000 L.D: The Second Generation Titan-Forged are first created.
2,000,000 L.D: Proto-Drakes are first created, their bodies comprised of metal or earth.
1,000,000 L.D: The Curse of Flesh corrupts many of the Titan-Forged creations, resulting in the Flesh-Cursed races. 
800,000 L.D: C'thalos creates Zithos, the Deity of Lightning as well as the realm of Anzreol. Though Zithos is expected to have begun receiving worshippers shortly before his creation, his first worshippers remain unknown.
700,000 L.D: C'thalos creates Sang, the Deity of Blood as well as the realm of Envar. Around the same time as his creation, Sang begins receiving worshippers from certain Troll tribes on Zandalar.
670,000 L.D: Cronoru begins receiving his first worshippers, at this time from the Bronze Dragonflight of southern Kalimdor.
650,000 L.D: Cataclysar begins receiving his first worshippers, at this time from certain Yaungol clans in the Pashidon region of Northern Alonia.
650,000 L.D: The Cataclysarian Era begins.
630,000 L.D: Nensimancy, a fusion between Cataclymancy and Terramancy, is first discovered within Southern Kalimdor by an unnamed Bronze Dragon. C'thalos then creates Nensis, the Deity of Sand as well as the realm of Setracaust.
600,000 L.D: The Cataclysarian Era ends.
500,000 L.D: Elune begins receiving her first worshippers, at this time in northern Kalimdor from the newly evolved Kaldorei.
400,000 L.D: Thraiomancy, a fusion between Keramancy and Cataclymancy, is first discovered by Vrykul of Eastern Veritia. C'thalos then creates Thrain, the Deity of Storm as well as the realm of Palhena. 
250,000 L.D: After the 6th Archon of Elune known as Orosai first discovers the astral magic fusion, C'thalos creates Omourel, the Deity of Stars as well as the realm of Stellenar. 
100,000 L.D: Zethroran, a risen druid in Reigazon Basin (now known as Icecrown) discovers Darakthemancy, a fusion of Nyrumancy and Mordellimancy. 
100,000 L.D: Zethroran becomes the first Archon of Pestilence, then discovering the existence of Darak'thenon. 
100,000 L.D: The Darak'thenian Era begins.
98,000 L.D: The Darak'thenian Era ends. 
50,000 L.D: Arthatos is first discovered by a village of Zandalari trolls, the trolls becoming his first worshippers.
1,460 L.D - Soveranos 25th: The Dark Portal is completed, and armies of the Old Horde pour through and into the Black Morass, marking the beginning of the First War. Members of the Twilight's Hammer Clan immediately senses the dark presence of the Old Gods upon entering Eliades, and occasionally hear whispers.
1,460 L.D - Soveranos 25th: The Frostwolf Clan, after expressing disgust toward Gul'dan and Blackhand's leadership, is banished from the Old Horde, resulting in a mass exodus north on Eliades to try and seek refuge.
1,460 L.D - Soveranos 26th: As the various human villages in the Black Morass are destroyed, Blackhand orders his armies north west, destroying every village in their path until eventually reaching Stormwind. This begins an encirclement of the city on all ends except the sea.
1,460 L.D - Soveranos 27th: The Bleeding Hollow Clan led by Kilrogg Deadeye embark on a separate campaign southwest into Stranglethorn, however after being met with a strong resistance by the Gurubashi Tribe they are forced to retreat.
1,460 L.D - Soveranos 30th: Sir Anduin Lothar and his armies flank the Old Horde armies surrounding Stormwind, and this engagement along with a coordinated response made by the city's forces result in the Old Horde being forced to retreat from Elwynn Forest.
1,459 L.D - ‡alenos 1st: The Old Horde regroups in Rockard, a fortress built close to the Dark Portal. Cho'gall and other members of the Twilight's Hammer clan continue to hear whispers of the Old Gods, however the voices have gradually gotten louder and louder. Cho'gall in secret establishes an allegiance to the Old Gods, considering them his clan's true allies in contrast to the Old Horde.
1,459 L.D - ‡alenos 2nd: The Old Horde, weakened by Stormwind, spend around two years to fortify what territory they did take. Blackhand expresses scorn to the Twilight's Hammer Clan for frequently disobeying orders, asserting that Stormwind would've fell if they listened. Blackhand also considers destroying the Twilight's Hammer Clan to make an example of their defiance. Cho'gall, the Twilight's Hammer Clan's de facto leader, offers to Blackhand to become the official leader to keep the clan in line, and Blackhand agrees. 
1,459 L.D - ‡alenos 7th: The Frostwolf Clan arrives in Alterac Valley, establishing it as their new home.
1,459 L.D - ‡alenos 10th: Thrall is born.
1,459 L.D - ‡alenos 11th: Shocked by Thrall's green skin, Durotan (Thrall's father) sends messages through the elements to meet with Orgrim Doomhammer near Loch Modan. The two meet to discuss this revelation and go their separate ways. Orgrim sends his most trusted friends with Durotan and his wife, Draka, for protection, but they turn out to be loyal to Gul'dan. They murder Durotan and Draka and leave Thrall for dead, but the infant is soon found by Aedelas Blackmoore.
1,458 L.D - Lœceros 22nd: Stonard is built, becoming one of the Old Horde's most important outposts.
1,457 L.D - Æveros 22nd: Bleeding Hollow spies report of an invasion being planned by the forces of Stormwind, resulting in the war once again heating up. Blackhand orders a number of arbitrary attacks on Stormwind villages to elicit uneasiness as well as to encourage the Stormwind invasion to be called off.
1,457 L.D - Æveros 30th: Blackhand sends the majority of his army into Redridge Mountains, managing to take control of the entire region after a bloody confrontation with Stormwind's armies. 
1,457 L.D - Saeqenos 1st: Cho'gall, under the influence of the Old Gods, suggests that the Old Horde utilizes their new passage into the Burning Steppes to inhabit Blackrock Mountain and establish it as their official capital. Blackhand disagrees out of desire to keep closer guard over the Dark Portal, however allows for the Twilight's Hammer Clan and the Shadow Council to make the travel north.
1,457 L.D - Saeqenos 11th: The Old Horde, after fortifying their new territory, attack Stormwind once more. It's met as a stalemate and the Horde retreat.
1,457 L.D - Icaros 8th: Garona Halforcen is allowed entrance to Stormwind by the word of Khadgar, who warns King Llane Wrynn about Medivh's fall to the Legion.
1,457 L.D - Icaros 15th: Khadgar and Garona go to confront Medivh and a battle ensues. Sargeras' spirit, still inside Medivh, magically ages Khadgar well past his prime. Gul'dan sees the battle through Garona's eyes and frantically connects with Medivh, mulling through the Guardian's memories for more details on the Tomb of Sargeras' location. Khadgar slays Medivh and Gul'dan is put into a coma. The death of Medivh, whose body was still infused with fel, caused a catastrophic explosion, scorching the land around Karazhan into Deadwind Pass and turning Brightwood into Duskwood.
1,457 L.D - Icaros 17th: Seeing the Shadow Council's weakness after Gul'dan's coma, Orgrim expressed his hatred to Blackhand for his cooperation with Gul'dan and thus challenged Blackhand to a mak'gora. The duel, located within Rockard, ends in Orgrim crushing Blackhand's skull with his family heirloom, the Doomhammer, and Orgrim becoming the new Warchief. This historical moment also marks the beginning of the Horde, as apart from the Old Horde.
1,457 L.D - Icaros 21st: Garona and Khadgar return to Stormwind to inform Llane of the Guardian's death. In the battle, however, Gul'dan had implanted thoughts of killing allies into Garona's mind. These messages flared bright in her head once more, and she assassinates Llane.
1,457 L.D - Icaros 25th: With the unforeseen death of Llane, the new Warchief saw it as the perfect opportunity to finally take Stormwind and prove himself to his men. This was certainly a necessary action to be taken being that some members of the Horde who were more loyal to Blackhand were skeptical of Orgrim's leadership abilities. Unlike previous attempts, the Horde's siege on Stormwind was a massive success. With concentrated attacks, the front gates managed to fall and the city was quickly sacked and then burned. As the city fell to fire, Lothar is forced to gather what refugees he can to flee north, marking the end of the First War.
2,622 V.R - ‡alenos 6th: Thrax Morzirus Dawnblade L is born.
2,636 V.R - ‡alenos 1st: Thrax Dawnblade kills his father, Septimus Dawnblade XLIX and becomes the 50th King of Valthiar.
2,644 V.R - Icaros 10th: The 3rd Valthian Areptorate begins.
2,660 V.R - Æveros 8th: Thrax Dawnblade is killed by Nibiru.