Timeline

• The Alterans (Ancients) evolve and progress to a scientific level far beyond that of present-day humanity.
• An ideological split appears between two factions of the Alterans: One progresses towards an increased belief in religion, the other towards belief in science. The Alterans who believe in science come to the Milky Way and settle on Earth. They colonize many planets and seed a network of Stargates throughout the galaxy, the oldest of which, the Antarctic Stargate, was planted on Earth 50 million years ago.

• The Alterans were confirmed to have originated from the Ori home galaxy in "Stargate: The Ark of Truth".

• Members of the Alterans in the Milky Way and in their home galaxy Ascend to a higher plane of existence.
• The ascended Alterans within the Milky Way, who are known as the Ancients, and the ascended Alterans within their home galaxy, who are known as the Ori, continue their ideological war across both the Ascended and lower planes. As the ascended Ori continue to interact with the lower planes they translate their sense of divine right into a very literal stance, and attempt to convert all sentient beings to a religion that centers around worshiping them, called Origin. Meanwhile, the ascended Alterans within the Milky Way gravitate towards a belief of free will and self-determination for all life.

• The Alterans within the Milky Way suffer from a devastating plague, possibly of Ori origin. Many try to reach ascension in order to escape it.
• Atlantis, the Alteran capital city within the Milky Way, departs for the Pegasus Galaxy via its stardrive. An Alteran named Aiyana is left behind and ends up frozen in ice.
• Once the city leaves, the Alterans activate the Dakara Superweapon to try and reseed life in the galaxy after the plague.

• The Alterans settle within the Pegasus galaxy, colonizing several worlds and instigating the evolution of humanity on others. Their people come to be known as the Lanteans, or the Ancestors to the seeded humans.
• The Lanteans seed a world home to the Iratus bug in the Pegasus Galaxy and the bug acquires human DNA, either through feeding on humans, or through the aforementioned genetic seeding. It rapidly evolves into a humanoid form, known as the Wraith.
• After the Wraith develop their numbers and technology to a sufficient level, they enter into war with the Lanteans. The Lanteans, with their vastly superior technology, win almost every battle, but due to the superior numbers of the Wraith which are created through the use of cloning powered by stolen ZPMs, cannot win the war.
• In their desperate search for better weapons against the Wraith, the Lanteans create an artificial life form known as the Asurans from nanite technology. However, the Asurans achieve sentience and throw off the yoke of their creators. The Lanteans attempt to destroy the Asurans, but fail.
• In the Milky Way galaxy, the Goa'uld and Unas evolve on P3X-888. The "second evolution" of humanity evolves on Earth.
• The Ascended within the Milky Way shield the galaxy from the Ori.
• The Asgard in the Ida galaxy begin exploring space within and outside their galaxy (c. 30,000 BC).
• The Goa'uld learn to take the Unas as hosts and to use the Stargate on their planet, which has been left there by the Alterans. They travel to other planets in these Unas hosts, conquering and multiplying.
• Due to their absence from the Milky Way Galaxy, and the extreme age of the technology which remains, those species which evolve after their exodus name the Alterans 'the Ancients'.
• The war between the Wraith and the Lanteans in the Pegasus galaxy escalates to the point where Atlantis is constantly under siege. The Lantean people decide to leave Atlantis for Earth by going through the Stargate. Atlantis, protected by a powerful force-shield, is sunk to the bottom of the ocean. The Lanteans leave Atlantis to find that the native peoples on Earth are quite primitive, preventing them from ever rebuilding their great civilization; the Lanteans then live out the rest of their lives with the native peoples.

• The Ancients on Earth go on to influence the language and mythology of Ancient Rome and the myths of Greece; their research on Ascension forms the basis of Buddhism. Many Ancients continue to use the Stargate network, and form an Alliance of Four Great Races, with the Nox, the Asgard and the Furlings, who have become very advanced. This Alliance lasts for centuries.
• The Goa'uld discover Earth and Humans, and abandon Unas as hosts. They take dominion over many areas of Earth, particularly Egypt, and pose as Gods.
• Alternate timeline: Elizabeth Weir is rescued from the ocean of Atlantis after accidentally travelling backwards in time from the year 2004, using an altered time-travel capable Puddle Jumper. She befriends the Ancient Janus, who programs Atlantis to rise from the ocean if the shields fail, blocks all but the Earth gate from making connections to Atlantis, and makes alterations so that instead of using the multiple remaining ZPMs in parallel, Atlantis uses the remaining ZPMs sequentially, and puts Weir in a cryonic sleep, to be automatically awoken when an active ZPM becomes drained so that she can exchange them; and to be found by her alternate self 10,000 years later.

• Humans become slaves and worship the Goa'uld. In Egypt, the theocracy founds Egyptian mythology.
• Various Goa'uld transport humans as slaves to other planets using the Stargates in order to increase their numbers. (This results in the Goa'uld affecting various other Earth mythologies.) In particular, ancient Egyptians are taken to the planet Abydos to work as slaves.
• Ra becomes the Supreme System Lord and the only Goa'uld ruling Earth.
• The last remaining Ancients either die out or Ascend.
• The Sodan, a faction of Jaffa, rebel against the System Lord Ishkur and free themselves. They start on a journey to find Kheb before settling on a hidden Ancient planet.
• Omoroca arrives on Earth and attempts to prevent the Goa'uld from securing domination over Humanity. The Goa'uld Belus kills Omoroca, though it has been theorized that her influence led to the eventual Human rebellion.

• The Humans of Earth rebel against the Goa'uld Ra, possibly instigated by the Oannes, and free themselves of his domination. The Stargate on Earth is buried and Human civilization begins its natural evolution.
• Alternate timeline:
  • SG-1 arrives in ancient Egypt via a time-traveling Puddle Jumper. They locate a ZPM that belongs to the ruling Goa'uld, Ra, and bury it. However, their actions upset causality severely.
  • SG-1 instigates an uprising against Ra, not wanting to live in servitude and hiding. The uprising is successful, causing Ra to leave Earth with the Stargate.
  • The future SG-1 came from has been drastically altered, primarily because Ra took the Stargate with him when he departed. Prepared for just such a possibility, SG-1 has left a message for the future; an alternate SG-1 minus their Daniel Jackson comes back to Egypt and helps the original Daniel Jackson fix the timeline. They instigate the rebellion again, and it is again successful, but this time Ra leaves without the Stargate, which is sealed in the sands of Giza. Ra goes to Abydos.

• The Ancient Moros, later known as Merlin, de-Ascends on earth, where he begins building a weapon to neutralize Ascended beings, the Sangraal. He befriends a group of knights and creates the basis for the Arthurian legends. An Ascended ancient, Morgan Le Fay, destroys the weapon but places Merlin in stasis, so that he may re-build it if the Ori ever threaten the Milky Way.

• Teal'c is born on an unspecified planet under Cronus' control.

• Germany discovers the DHD at Giza. They possess it until the end of World War II when the invading Soviets discover it and take it to Russia.

• Archaeologists at Giza find the Stargate buried 5,000 years ago by the Egyptian rebellion. Eventually it comes into the possession of the USA, where the military conducts experiments with it.

• Researchers manage to activate the Stargate, and Dr. Ernest Littlefield, fiancé of Catherine Langford, travels through. He is not able to return until 52 years later, when he is discovered and rescued by SG-1. The military canceled the experiments after his disappearance. Some time after this the Stargate is moved to an armory and locked away.

• Jonathan 'Jack' O'Neill is born in Chicago, Illinois, USA on October 20.

• Daniel Jackson is born in Olympia, Greece on July 8.

• Samantha 'Sam' Carter is born in the US on December 29.
• Rodney McKay is born in Canada on an unspecified date.

In the Atlantis Season 4 episode "Quarantine" Rodney's year of birth is discussed whilst Sheppard recalls Rodney's password.

• SG-1 arrive in 1969 after being sent back in time from March 1999, by a freak accident involving a Stargate's wormhole passing through a solar flare. They meet a young George Hammond, who helps them get back to the future. Teal'c also learns to drive.

• Cameron 'Cam' Mitchell is born.

• Archaeologists Claire and Melbourn Jackson are crushed by an Egyptian coverstone while it is being moved in a museum. This is witnessed by their eight-year-old son, Daniel Jackson, and remains one of the most powerful and traumatic moments in his life.

• Jack O'Neill's son Charlie accidentally shoots himself with Jack's gun and dies. Jack and his wife Sara split up and Jack becomes depressed and suicidal due to the loss of their child.

• Events of the film:
  • Daniel Jackson, now a brilliant Egyptologist and linguist, but shunned from the academic world due to his farfetched theories about the construction of the pyramids, gives a lecture on such a theory. As it fails, Catherine Langford contacts him and takes him to Cheyenne Mountain to aid in the deciphering of strange hieroglyphs that were found on the cover-stones of the still-enigmatic Stargate.
  • Jackson realises they are not hieroglyphs but constellations, such that seven can plot a course through space. The Stargate is revealed to him, and he figures out the seventh symbol to complete a dialing address to the planet Abydos. Jack O'Neil commands a team, with Jackson as interpreter, and they step through the gate. O'Neil is given a secret order to detonate a large nuclear bomb on the other side if there is any threat.
  • On the other side they discover the descendants of Ra's slaves, the Abydonian people. Daniel is married to a native, Shau'ri, as a gift, although he doesn't realise what happened until later.
  • When Ra realises they have come he attacks and captures the members of the Earth exploration team that remained with the Stargate. There is a further problem — the cover stones on this side are broken and Jackson can't find the seventh symbol needed to dial home. O'Neil tries to detonate his bomb but finds it has been taken by the Goa'uld; Ra's guards capture O'Neil and Jackson.
  • Native Abydonians, including Skaara, help Daniel and O'Neil escape. When Daniel works out the seventh symbol, they hatch a plan to reach the gate before Ra uses it to send O'Neil's nuclear bomb back to Earth, enriched with the mineral that is mined on the planet — the result would be apocalyptic. Ultimately, after they have overpowered Ra's guards, Ra tries to escape in his ship, but O'Neil Rings the bomb onto his ship, where it detonates in space and kills Ra, freeing the Abydonian people.
  • Daniel Jackson helps O'Neil dial home, but stays on Abydos after having fallen in love with his wife Shau'ri.
• Subsequent events:
  • O'Neil returns to Earth and files a false report that Daniel Jackson was killed and that the Abydonian gate was destroyed. He finally retires.

• Colonel Jack O'Neill's name was spelled O'Neil.
• Colonel Jack O'Neill's wife/ex-wife was named Sarah rather than Sara.
• Colonel Jack O'Neil's son was named Tyler rather than Charlie.
• Dr. Jackson's wife's name was Sha'uri, rather than Sha're.
• The Stargate was housed in the Creek Mountain rather than the Cheyenne Mountain complex.

• Believing the Stargate to no longer be a threat, the military files it away as a relic.

• Apophis, Ra's enemy and also a Goa'uld System Lord, is looking for potential hosts for his Queen, Amonet. He sends a small attack force through the gate, killing a few guards at Cheyenne Mountain and taking a female guard back through the gate.
• George Hammond, the present commander of Cheyenne Mountain, calls in Jack O'Neill, who is forced to admit the truth about the Abydos stargate. Samantha Carter joins the base, and forms a part of O'Neill's team.
• O'Neill returns to Abydos and relocates Daniel Jackson. They find a catacomb engraved with thousands of gate addresses, realising that there are more than two gates — that there is, in fact, a huge network.
• Apophis captures Skaara and Daniel's wife, Sha're (formerly spelled Sha'uri in the film). Daniel leaves the Abydonians to search for her and bring her back.
• They are captured on Chulak and will soon be executed; however, Apophis' First Prime, Teal'c defects to their cause and helps them escape.
• Sha're is taken host by Amonet and Skaara by Apophis' son, Klorel.
• On returning to Earth, the base is dubbed Stargate Command, and SG teams are created to use the gate to find technology and allies to fight the new threat of the Goa'uld. Daniel Jackson decides to join the SGC's quest, so that he can find and save his wife and his brother-in-law Skaara.
• The Iris protecting the base against unauthorized inbound travelers is installed.
• Daniel Jackson, Teal'c, Samantha Carter and Jack O'Neill become official members of the primary SG team — SG-1.

• SG-1 bring a plague back to the SGC.

• SG-1 encounter the Nox, one of the Four Great Races.
• SG-1 encounter the Asgard, one of the Four Great Races.

• Daniel Jackson realises that Ernest Littlefield went through the gate in 1945 and never returned. SG-1 go on a mission to rescue him with Catherine Langford. He is brought back home and reunited with her, but whilst they were there Daniel Jackson learns about the Four Great Races.

• SG-1 encounter the Tollan, and Narim befriends Carter.

• SG-1 find a second Stargate and DHD left by the Ancients in Antarctica.

• Daniel Jackson encounters the Quantum Mirror, which brings him to an alternate reality where Apophis has attacked Earth — thus suggesting that the same will happen in this reality.
• Robert Kinsey tries to shut down the SGC as it is too great a threat, ignoring Jackson's warnings.

• SG-1 disobey orders and use the Stargate to travel to one of the two Ha'tak attack vessels that Apophis is attacking in. Skaara/Klorel is in control of it. They fill the ship with tactical C4, and although they are not able to save Skaara, they avert the attack, and both Apophis and Skaara get away.

• The Tok'ra Jolinar possesses Sam, but ultimately sacrifices itself to save her life. Sam is left with pieces of Jolinar imprinted onto her, including an ability to sense other Goa'uld.

• Daniel Jackson returns to Abydos, fulfilling a promise that he would return in one year. There, he discovers that Sha're has been returned by Apophis, as she is pregnant and he wants her safe from his enemies; one effect of the pregnancy is that Amonet is subdued and not in complete control. For the moment, Daniel Jackson is reunited with his wife; he later delivers the baby. Once this happens, Amonet regains control but is incapacitated by Teal'c, who is dressed a Horus Guard (the guardians of the family of Ra). She later returns to Apophis, and tells him that a rival Goa'uld System Lord, Heru-ur, took the child, having recognised Teal'c's armour. The child is given to Sha're's father, and they go into hiding.

• SG-1 formally meet the Tok'ra, and befriend them; Sam's father Jacob blends with one of their symbiotes named Selmak.
• Rogue NID agents are discovered to have been operating illegally to steal alien technology indiscriminately for the safety of Earth.

• Jack encounters a Repository of the Ancients and has Ancient knowledge downloaded into his brain, leading to him creating a power-source capable of allowing the Stargate to dial 8 chevrons and connect to the Asgard home galaxy. He befriends the Asgard in person, and they realign his mind before sending him back.

• Apophis is defeated by another powerful Goa'uld, Sokar. He crash-lands, and when SG-1 find him, he is so badly wounded he asks for sanctuary on Earth; SG-1 reluctantly grants it to him. When Sokar finds out that the Tau'ri are holding Apophis, he begins to attack Earth; he will stop on the condition that Apophis is handed over to him. Apophis dies, and the SGC hands his body over to Sokar.
• Sokar later uses a Sarcophagus to revive Apophis and torture him indefinitely.

• Hathor captures and tricks SG-1. She makes each of them believe that they have woken up alone at the SGC, 79 years in the future. SG-1 quickly figure out what's going on, and Jack kills Hathor. With the help of several SG teams, the Tok'ra and Jaffa, they defeat Hathor's army and escape home.

• With the help of the Asgard, SG-1 negotiate with the System Lords to bring them into the Protected Planets Treaty. Although the negotiations are successful in preventing the Goa'uld from attacking Earth, the treaty does not protect SG teams on other planets.

• Daniel Jackson finds Sha're, still possessed by Amonet. Amonet captures him and tries to kill him. Teal'c steps in at the last minute, and is forced to kill Sha're to stop Amonet. In the last moments of her life, Sha're manages to transfer a message to her husband that he experiences in a set of visions. She tells him where her son, the Harcesis, is; Daniel can and must now find this boy, who has the knowledge and power to defeat the Goa'uld.
• While trying to rescue the Tok'ra Jacob Carter, SG-1 is captured by Sokar on his prison world, but manage to escape. One of Sokar's underlings reveals himself to be Apophis; who kills Sokar and takes control of his armies.

• Klorel, Apophis' son in the body of Skaara, crash-lands on Tollana. A trial (called triad) is held to determine as to who has the right to possess the body, with Daniel and Jack defending Skaara. It is decided in Skaara's favour. Skaara is finally freed of Klorel, and is infinitely grateful to Daniel and Jack; he returns to his homeland Abydos. After the trial, the Goa'uld disable every Ion Cannon at once so their ships can destroy Tollana; however, Teal'c and Lya of the Nox save one by cloaking it, and use it to destroy the Goa'uld attack force.