Building a timeline for the original manga is possible if you read the manga carefully and because there are two clear dates. The first one is the newspaper date announcing the Galaxian Wars which is Sept. 10, 1986. The second one is Julian's birthday party and his birthday is Mar 21st. By using those two dates, the whole original manga happened between Sept. '86 to Apr. '87. To keep things simple, it is better to use the 86 year as a base point to start building your timeline. The following timeline is built based on the manga, Saint Seiya Encyclopedia and the Hypermyth. The references in the brackets are denoting the Jump Comics Book Volumes[i.e. Vol. 1, p. 1], the Hypermyth[HM] and Saint Seiya Encyclopedia[EN] like Character Data. General History is also used to keep things in order.

The Original Manga Timeline

15 Billion years from the present - The Big Bang [Vol. 1, p. 56; HM]

The First Holy War[HM, Vol. 1, p 25. Vol. 18, p. 41-42. EN]

• Poseidon warred with Athena for the Land.[HM]

• Athena sent few Saints to guard Athena's Jar which contained the Spirit of Poseidon in the Artic Regions.[HM, Vol. 18, p. 36]

• Seven Generations after the First Holy War, the Athena Temple and the 12 Temples and other structures were built in Athens. Sanctuary was established.[HM]

• Few thousand years from the present, another Poseidon and Athena Struggle. Athena wins again, seals his Spirit in Athena's Jar in Under Sea Temple under the Mediterranean, and his Halberd inside the Cape Sounion Prision. Poseidon will not fight with Athena until the present time.[Vol. 18, p. 28, 41. EN]

• By Zeus's Will, Hades bought Gigas Giants from the world before the Big Bang. Athena and the Saints fought with them.[HM, Vol 1, p. 25.]

• Mu Continent was sunk, with little islands left. The skills of creating and repairing Cloths were left to only a few.[HM]

• The 58 Saints(included are the 4 Mysterious Saints) fights the 4 Armies of Berserkers.[HM]

• A Pegasus Saint looking like Seiya with his Cloth tainted with Athena's Blood invoked a God Cloth. Hypnos and Thanatos witness this one time occurence.[Vol. 26, p. 108-109. Vol. 28, p. 25-33]

• Hades fought with the Pegasus Saint and got wounded. From then on, he gets Hypnos to put his real body to sleep in Elysion ever after. After that, he chose an incarnation to possess in the future. [Vol. 26, p. 108-109. Vol. 28, p. 105-106, 146-148. EN.]

• A Saint discovered an island left from the Mu continent and later was called, Death Queen Island. Black Cloths was discovered there. Later, it was sealed by Athena. From here on there after, a Saint would have a Mask put on him to seal off Death Queen Island in each generation. The Black Saints were limited to the island.[HM]

• "Shaka" the Original Buddha, awakened the Super Sense. [HM; Vol. 10, p. 33; Vol. 21, p. 87.]

• The Saints secretly helped the Fall of the Roman Empire. [Vol. 1, p. 109; General History.]

• The Saints secretly defeated the Mongol Empire from invading Japan.[Vol. 1, p. 109; General History.]

1812 - Napoleon's Defeat

• The Saints secretly helped the collapse of the Napoleonic Rule. [Vol. 1, p. 109; General History.]

• 9-1, Athena came again at Athena Statue.[Vol. 13, p. 47; HM; Character Data]
• Pope Sion noticed the omen the previous Pope also noticed 230 years ago on Star Hill.[Vol. 13, p. 50]
• Gemini Saga killed Pope Sion for noticing the evil in him. And from here on, Saga gained what he wanted, and started to pretend to be the Pope. The Gemini Saint became 'missing'.[HM; Vol. 13, p. 28, 44]
• Athena's Cosmo saved Kanon from drowning. Kanon discovered Poseidon's Halberd, went to the Under Sea Temple and broke Athena's Seal. Poseidon who planned to sleep for an extra 200 or 300 years was awakened early. Poseidon went to sleep in 3 year old Julian and don't wake Poseidon until Julian turns 16. Kanon got his Sea Dragon Scale. Kanon put Athena's Jar inside Main Breadwinner.[Vol. 18, p.29-45, 132-133, 135.]
• Saga tried to kill baby Athena with his Golden Dagger. [Vol. 7, p. 145; Vol. 22, p. 39.]
• Aiolos entrusted baby Athena and Sagittarius Gold Cloth and Athena's Cane to Mitsumasa Kido, the President of Asia's most powerful foundation, the Graude Foundation and Aiolos died. Already having nearly 100 children he accepted his destiny that he has to sacrifice his children and treat them like Orphans. Mistumasa went back to Japan with Athena, and named her Saori Kido, raised her like a grand-daughter and changed the Sagittarus Gold Cloth's shape and said to people, it was an antique he got from Northern Europe.[Vol. 6, p. 101, Vol. 7, p. 150, 168-169.]
• Some weird power opens the lock to the cottage. Pandora took off Athena's Seal and the subjects of Hades, Hypnos and Thanatos were free.[Vol. 27, p. 30-34]
• 9-9, Shun was born in Japan. Pandora's mother gave birth to Hades's spirit. Hypnos and Thanatos instructed her to go to Japan because Hades has chosen one of the Orphans in Japan to be his incarnation in this time, Shun. However, upon seeing Ikki protecting Shun with a passion like fire, afraid that Hades might be hurt as a result, she decided not to put Hades's Spirit into Shun. Instead, she puts the pendant, "Yours Ever" on Shun, intent on binding him to Hades. Pandora closed half of that memory in Ikki. Later, Ikki without full memory, told Shun that, the pendant must be left by their mother... [Vol. 25, p. 47-57; Vol. 27, p. 30-42; Vol. 23, p. 33. Character Data]

• Hyoga's Mama, Natassia traveled with him to Japan, but the ship sunk with her. Hyoga arrived in Japan but got treated by Kido as just one of the Orphans.[Vol. 6, p. 89; Vol. 4, p. 56; Vol. 8, p. 45]

• Graude Foundation gathered all of the 100 Orphans/half-brothers. They were gradually send to each of their training places.[Vol. 3, p.20-21, Vol. 5, p. 100]
• Luckily, Hyoga got sent to Siberia near Mama to be trained with Camus and Isac.[Vol. 6, p. 90; Vol. 16, p.152]
• Shun got sent to Andromeda Island to be trained with Cepheus Daidaros and Chameleon June and others.[Vol. 5, p. 65. Character Data.]
• Ikki got sent to Death Queen Island in place of Shun and trained(tortured) by Guilty. [Vol. 5, p. 73.]
• Shiryu got sent to 5 Old Peaks, Mt. Ro in China to be trained by Roshi and meets Shunrei.[Vol. 9, p. 84]
• Seiya got sent to Sanctuary, Greece to be trained with Eagle Marin. The day Seiya went to Greece was the day Seika became missing. Seika heads for Sanctuary, but fell over a cliff. An old man saved her but she got amnesia. She only knew her name was Seika from her belongings. She stayed there over the years to help in the old man's store, at Rodorio Village.[Vol. 1, p. 43, 136, Vol. 27, p. 97-98.]

• After telling Saori the truth about her idenity and the real reason behind Galaixan Wars, Mitsumasa died. She became the President of the Graude Foundation.[Vol. 7, p. 150]

• For the first time, Hyoga successfully broke the Ice Ground. Hyoga dove in and headed for his Mama's ship. Hyoga got caught in the current. Isac saved Hyoga, but lost his eyesight in his left eye in the process, and he encountered the Kraken. Poseidon's Strong Will saved Isac and he later became a Marina...[Vol. 16, p.166-175]

• The Galaxian Wars
• The Black Fights
• The Silver Fights

Apr 5th, 1987 - The Poseidon War -

Apr 6th, 1987 - The Hades War, Defense -

Apr 7th, 1987 - The *REAL* Hades War, Attack -

Time matters

• 3-21-1987 - Julian's party[Vol. 14, p. 8]
• 4-5-1987 - 13 days later, Tetis tries to abduct Saori. 4 boys still coma because of one month ago battle. The doctor says the 12 Palaces Battle was one month ago.[Vol. 14, p.34-40, 50]
• 3-5-1987 - 12 Palace Battle
• 4-6-1987 - Since Ichi and Nachi discuss Saori was just coming back from drowning in the beginning of Hades Chapter, so the next day can be the beginning of Hades War.[Vol. 19, p. 14]

    First, unlike the manga, the original TV Series never declared what year it was. Also, many of the outside stories don't fit with the main timeline of the anime. With ND claiming the year is 1990 actually makes no sense at all. But for those who need to know, this section tells you the issues you have to consider to try to fit all the timelines.

Cygnus Story

    The manga should happen after Sanctuary Chapter because Hyoga knows Aurora Execution but Hyoga is wearing original Bronze...

Movies

• Movie 1 Eris, 2 Asegard should happen after they learn the 7th Sense but they are still wearing original Bronze.
• Movie 3 Abel, 4 Satan should happen after Poseidon but their Cloths are not broken and Shiryu can see like normal.
• Movie 5 Overture happens after Hades Chapter with the introduction manga drawn by Masami happening right before the movie.

• Side Story 1 should happen after Docrates is defeated but Shun and Ikki are wearing New Cloths.
• For Side Story 2, the story begins 14 years ago from the present and ends at 13 years ago.
• Side Story 3 happens between Sanctuary and Asgard anime.

    The present era Gigantomachia battle doesn't fit in the timeline because the author said it is another interpretation of Saint Seiya but if you force it to fit since the story happens in summer time the only summer that makes sense is the one after Hades, since all the events in the original manga happened from Sept. 86 to Apr. 87.

LC, Ep. G

1800 Century - LC -

7 Years ago, 1979 - Ep. G -

1986-1987 - Original Manga Timeline -

ND

    The story of ND happens right after the Hades War and 243 years ago from 1990, so:

1747 - Previous Era Story

1989 - 1990 Original Manga Timeline + 3 years

1990 - Present Era Story

Omega

    In Figure Ou Magazine and Pia, it is stated that time frame for Omega is 10 and a few years after the previous show.