Stargate Timelines

Stargate Franchise Timeline Analysis

A Consolidated Guide to Alternate Timelines

Part One: The Rules of Time Travel in Stargate

Before mapping the timelines themselves it is essential to understand the mechanics of time travel as established across the franchise. These rules shape how each timeline change works and why.

Rule 1 — The Stargate and Solar Flares

The first time travel in the franchise is accidental, caused by the Stargate interacting with a solar flare. This establishes two foundational facts: the Stargate can send travelers backward in time, and it can also send them forward. This mechanism reappears in later episodes and is distinct from other time travel methods introduced later in the series.

Rule 2 — The Ancient Time Machine

Separate from the Stargate, a time machine built by the Ancients is introduced in later episodes. Like the Stargate method, it is capable of travel both backward and forward in time. It operates independently of the Stargate network, and its effects on timelines may differ from Stargate-facilitated time travel in important ways.

Rule 3 — Alternate Dimensions vs. Alternate Timelines

At the end of SG-1's first season the franchise introduces the concept of alternate dimensions. These are distinct from alternate timelines. Alternate dimensions represent the infinite variations of choices that could have been made — parallel realities running alongside the prime dimension. Within these dimensions characters are generally true to their core nature, though occasionally extreme divergences occur.

Alternate timelines, by contrast, are sequential replacements of a single dimension's history. A new timeline does not run in parallel — it replaces its predecessor within the same dimension.

Rule 4 — One Permanent Timeline Per Dimension (The Continuum Rule)

Stargate Continuum establishes the most important rule in the franchise: a single dimension can only sustain one permanent timeline. When Ba'al travels back in time to alter history he does not simply branch off a new timeline — he overwrites the existing one. The old timeline does not persist alongside the new one. It begins to disintegrate.

This disintegration is not instantaneous. There appears to be a window of time between the moment of change and the complete erasure of the old timeline — something like a ripple spreading outward from the point of alteration until it reaches the ends of history. During this window individuals in the old timeline can still act.

Rule 5 — Stargate Transit During Timeline Collapse

Continuum also establishes a critical survival mechanism: any individual who passes through a Stargate while the old timeline is collapsing is shunted into the new timeline. This appears to function regardless of which Stargate is used. In the film Ba'al creates his new timeline from a hidden Stargate on a remote planet while SG-1 transitions to the new timeline by traveling from the Tok'ra homeworld to Earth. Both jumps produce the same result: arrival in the new timeline.

Whether a similar transit effect applies to the Ancient time machine remains unknown, as we have not yet seen a direct comparison.

Rule 6 — The Progression Threshold

Not all timeline changes produce equally dramatic divergences. Some changes are so minor that the resulting timeline follows nearly the same course as its predecessor with only subtle differences. Others produce radical departures. The theory of a progression threshold suggests that small cumulative changes across successive timelines eventually reach a tipping point, beyond which further change produces a dramatically different result.

This concept helps explain why certain timeline-replacement events look almost identical to their predecessors while others diverge completely. It also provides a framework for understanding cases like the episode 1969, where a seemingly closed loop may have involved two near-identical timelines that were close enough to function as one from a narrative standpoint.

Part Two: Contained and Bubble Timelines

Not every time travel event in the franchise produces a new permanent timeline. Some are localized — changes that occur within a bounded region or period and do not propagate to universal scale. These are called bubble timelines. Two key examples illustrate this concept, and they form an instructive pair.

Window of Opportunity — SG-1, Season 4, Episode 6

Jack O'Neill, Teal'c, and the alien scientist Malachi are caught in a time loop caused by a device activated near a Stargate. The loop lasts approximately six hours before resetting. We are told the bubble remained in effect for at least three months — likely longer. At an average of roughly 730 hours per month, three months of six-hour loops produces a minimum of approximately 365 contained timelines, all beginning and ending on the same day within the bubble.

Each loop technically constitutes a new timeline under the Continuum Rule, but all are contained within the bubble and do not propagate outward to universal scale. The prime timeline resumes at the end as though nothing occurred.

The one lasting effect is informational. Jack, Teal'c, and Malachi retain their memories from each loop because of their direct contact with the device. Nobody else does, and no physical changes cross over. Their bodies reset with each loop just as everyone else's do — only the knowledge persists.

Unending — SG-1, Season 10, Episode 20

The Odyssey becomes caught in a time dilation bubble. Within this bubble a full lifetime passes for the crew while the outside universe remains effectively paused. This creates a contained timeline — designated T9b — sitting inside the broader permanent timeline T9.

Unending is a closer match to Window of Opportunity than it might initially appear: both are bubble timelines, and in both cases the prime universal timeline is not permanently replaced. However Unending is the heavier case in two significant ways. First, the memories that cross over represent not a few looped hours but decades of lived experience. Second — and more importantly — Teal'c's physical body also crosses over. He exits the bubble as a visibly older man. Something tangible and irreversible transferred from the bubble timeline into the prime timeline.

This raises an interesting question about where Unending sits relative to the Continuum Rule. If physical matter — a person's aged body — can transfer out of a bubble timeline into the prime timeline, the mechanism begins to resemble what happens in Continuum when SG-1 is shunted into the new timeline as their old one collapses. The difference is scale: Unending's bubble affects one person while Continuum rewrites all of history. But the underlying principle may be more similar than it first appears.

The Spectrum of Bubble Timeline Bleed

Taken together, Window of Opportunity and Unending define a spectrum of how much a bubble timeline can bleed into the prime:

Window of Opportunity — memories only, for individuals connected to the device. Bodies reset. Prime timeline physically unchanged.

Unending — memories and physical state both cross over, for one individual. The prime timeline now contains a Teal'c whose body should not exist in it by any prior chain of causation.

The threshold between these two cases — what determines whether only memories transfer or whether physical matter transfers as well — has not been explicitly addressed in the franchise and remains an open question.

Part Three: The SG-1 and Film Timelines in Detail

T1 — The Stargate Origins Timeline

The earliest known timeline in the franchise. Stargate Origins shows us events surrounding the discovery and early use of the Stargate in the late 1930s. There are notable differences between Origins and both the Stargate film and SG-1. Rather than treating these as continuity errors, they are best understood as evidence that Origins occupies its own distinct timeline — the earliest anchor point in the chain. The divergence that separates T1 from T2 is unknown, as is the year it occurred.

Note: because all events surrounding this timeline and it divergence are unknown, it could technically end up anywhere on the list.

T2 — The Stargate Film Timeline

The original 1994 Stargate film occupies a timeline distinct from the SG-1 television series. The differences between the film's portrayal of characters, the Stargate program, and various details of the mythology are significant enough to suggest at least one timeline change separates the film from the series. T2 diverges from T1 at an unknown point and for unknown reasons. The progression threshold framework suggests the changes were minor enough not to dramatically alter the broad shape of events — the Stargate is still discovered, Ra is still defeated — but specific details differ.

Note: because all events surrounding this timeline and it divergence are unknown, it could technically end up anywhere on the list. But, due to its primacy in the real world, it is assumed to be an earlier timeline.

T3 — The SG-1 Series Timeline

The timeline in which SG-1 begins. It diverges from T2 at an unknown point, again likely a minor progression threshold change given the broad similarity between the film's events and the series' backstory. T3 is the baseline from which the first explicit in-series time travel event branches.

T4 — The 1969 Timeline

SG-1, Season 2, Episode 21. In 1999 SG-1 is accidentally sent back in time to 1969 via Stargate and solar flare interaction. Under the Continuum Rule, the moment they arrive in 1969 T3 begins to disintegrate and T4 takes its place. T4 starts in 1969 and diverges from T3 in 1999.

From inside the episode the events appear to form a closed loop — they travel back, navigate 1969, jump to the future, and return to their correct era. Nothing appears changed. This is best explained by the progression threshold: the changes introduced during the 1969 visit were so minimal that T4 is nearly indistinguishable from T3. It functions as a closed loop in practice even if two technically distinct timelines exist.

T5 — The Cassandra Divergence Timeline

T4 does not run all the way to the 2010 episode without at least one further change. At an undisclosed future date SG-1's encounter with Cassandra creates another divergence point. T5 diverges from T4 at this unknown future date and starts in 1999 — the same year as T4's divergence point, suggesting the two timelines share the same early history up to the Cassandra encounter before branching.

All of Window of Opportunity's approximately 365 or more contained bubble timelines fall within T5. They begin and end in the year 2000 without affecting the broader universal timeline. Jack, Teal'c, and Malachi carry the accumulated memories of those loops forward, but T5 itself continues unaltered.

T6 — The 2010 Timeline

SG-1, Season 4, Episode 16. T5 runs forward until the year 2010, at which point a group of SG-1 members — living in a future where the Aschen have allied with Earth and are secretly sterilizing the population — sends a warning back through the Stargate to the year 2001. T5 immediately begins to collapse. T6 diverges in 2010 and starts in 2001. It is the timeline in which the subsequent seasons of SG-1 take place and the one that continues into the early events of Stargate Atlantis.

T7 — The Before I Sleep Timeline

Atlantis, Season 1, Episode 15. T6 runs forward to 2005, at which point the Atlantis Expedition arrives in the city and — in the original version of events — most of them die. Dr. Weir uses the Ancient time machine to travel back approximately ten thousand years and intervenes, arranging for power, supplies, and information to be waiting for the expedition's eventual return. T7 diverges in 2005 and starts roughly ten thousand years in the past.

This means the Atlantis we see from the very first episode of that series is already operating in T7. Every SG-1 crossover episode during the Atlantis run takes place in a timeline shaped by Weir's ten-thousand-year-old sacrifice.

T8 — The Moebius Part 1 Timeline

SG-1, Season 8, Episodes 19 and 20. T7 runs from ten thousand years in the past through to 2005, at which point SG-1 travels back to ancient Egypt to retrieve a ZPM before Ra takes it offworld. This action diverges T8 from T7 in 2005, with T8 starting approximately three thousand years in the past. In T8 the Stargate is not discovered at the regular time — a major threshold crossing that dramatically alters the shape of modern history. The Stargate program never begins.

T9 — The Moebius Part 2 Timeline

The resolution of Moebius creates T9, which also diverges from the prior timeline in 2005 and starts approximately three thousand years in the past. Events in T9 largely follow the general shape of what came before with two meaningful signals that it is not identical to T7: a ZPM is discovered buried in Egypt, placed there by SG-1 from the previous timelines, and the pond next to Jack O'Neill's cabin — a running gag throughout the series for never having fish — now has fish. A small but deliberate marker of divergence.

T9b — Unending (Contained Bubble)

SG-1, Season 10, Episode 20. A contained bubble timeline sitting within T9. The Odyssey is caught in a time dilation field and the crew lives out decades inside it. Teal'c's memories of those decades and his physically aged body both cross over into T9 when the bubble collapses. T9 continues as the permanent universal timeline, now carrying a Teal'c whose body has aged far beyond what T9's causal chain would have produced. See Part Two for full discussion.

T10 — The Last Man Timeline

Atlantis, Season 4, Episode 20. T9 runs from three thousand years in the past all the way forward to approximately 48,800 years in the future, at which point Colonel Shepherd — stranded in a ruined future where the Atlantis Expedition has been destroyed — is sent back in time to 2008. T10 diverges approximately 48,800 years in the future and starts in 2008. In T10 the Expedition is not destroyed and the mission continues.

T11 — The Continuum Ba'al Timeline

Stargate Continuum. T10 runs from 2008 forward to the events of the film, at which point Ba'al — the last surviving Goa'uld System Lord — uses a hidden Stargate to travel back to 1939 and prevent the original Stargate from ever being discovered by the Allies. T10 begins to disintegrate. T11 diverges in 2008 and starts in 1939. In T11 the Goa'uld never fell, Earth was never defended, and Ba'al rules. SG-1 members are shunted into T11 as their original timeline crumbles.

T12 — The Continuum Resolution Timeline

The resolution of Stargate Continuum creates T12. Colonel Mitchell travels back to 1929 — ten years before Ba'al's intervention — and corrects the course of history. T12 diverges in 2008 and starts in 1929. It restores something close to the prior history with one permanent alteration: the future version of Cameron Mitchell, having been stranded in the past during the film's events, grows old in that era and lives out his life alongside his grandfather. T12 is the timeline at the end of all SG-1 and Stargate Atlantis events.

T13 — The SGU Time First Timeline

SGU, Season 1, Episode 8. Unlike most time travel episodes in the franchise, Time does not begin in the original timeline. By the time the episode opens we are already in T13 — the second timeline of this episode's sequence. A recording and a human skeleton provide evidence of T12's continuation, in which the crew encountered a deadly pathogen on a planet and died. Information from that first version of events was sent back through a Stargate via solar flare, creating T13. T13 diverges from T12 in 2009 and starts at an unknown point in the past — far enough back for a skeleton to form.

T14 — The SGU Time Second Timeline

The episode Time ends in T14, a third timeline created when information is again sent back from T13. T14 also diverges in 2009 and starts at roughly the same unknown point in the past as T13. The progression of knowledge through successive collapsing timelines is the central mechanism of this episode — each iteration sends more information back, allowing the crew to make better choices in the next.

T15 — The Twin Destinies Timeline

SGU, Season 2, Episode 12. T14 runs forward to 2011, at which point the crew of the Destiny attempts to use the ship's Stargate to dial Earth through a star. The attempt sends the Destiny itself back in time by several hours. Most of the crew aboard, however, are sent approximately two thousand years into the past. T15 diverges in 2011 and starts around 9 AD.

Applying the Continuum Rule: once a timeline is ruptured, anyone passing through a Stargate is shunted into the new timeline regardless of the specific Stargate used or the distance of the temporal jump. This means both the crew sent back two thousand years and the Destiny sent back mere hours end up in the same new timeline despite the vast difference in displacement. T15 is the current final timeline of the franchise and presumably the one in which any upcoming Stargate series will begin.

Part Four: Complete Timeline Reference

The following table lists every known timeline in the franchise in the order it appears, with the year it diverges from the previous timeline, the year it starts, its source episode or film, and key notes.

Timeline

Diverges

Starts

Source

Notes

T1

Unknown

Unknown

Stargate Origins

Earliest known timeline. Divergence details unknown.

T2

Unknown

Unknown

Stargate (1994 film)

Film diverges from Origins at unknown point. Differences suggest at least one progression threshold change.

T3

Unknown

Unknown

SG-1 Series Start

Series diverges from film at unknown point. Broad events similar; specific details differ.

T4

1999

1969

SG-1 S2E21 — 1969

SG-1 sent back via Stargate/solar flare. Near-identical to T3; likely a progression threshold event.

T5

Unknown future date

1999

SG-1 — Cassandra encounter

Divergence year unknown. Contains Window of Opportunity's ~365+ bubble timelines (year 2000), none of which affect the universal timeline.

T6

2010

2001

SG-1 S4E16 — 2010

Warning sent back from 2010 to 2001. T5 erased. Main SG-1 seasons and early Atlantis run in this timeline.

T7

2005

~8000 BC

Atlantis S1E15 — Before I Sleep

Dr. Weir travels back 10,000 years to save the Expedition. T6 erased. All of Atlantis takes place in T7 or later.

T8

2005

~3000 BC

SG-1 S8E19 — Moebius Pt. 1

SG-1 travels to ancient Egypt. T7 erased. Stargate not discovered on schedule — major threshold crossing.

T9

2005

~3000 BC

SG-1 S8E20 — Moebius Pt. 2

T8 erased. ZPM hidden in Egypt; Jack's pond now has fish. Small but deliberate markers of divergence from T7.

T9b

~2007

~2007

SG-1 S10E20 — Unending

Contained bubble within T9. Teal'c's memories AND physical age cross over. T9 remains the permanent universal timeline.

T10

~48,800 AD

2008

Atlantis S4E20 — The Last Man

Shepherd sent back from far future to 2008. T9 erased. Atlantis Expedition survives.

T11

2008

1939

Stargate Continuum

Ba'al travels to 1939 to prevent Stargate discovery. T10 erased. Goa'uld rule restored.

T12

2008

1929

Stargate Continuum

Mitchell corrects history. T11 erased. Future Mitchell stranded in past and lives out his life there.

T13

2009

Unknown past

SGU S1E8 — Time

Episode opens in T13. T12 crew died from pathogen; their recording created this timeline. Skeleton found.

T14

2009

Unknown past

SGU S1E8 — Time

T13 erased. Information from both prior timelines carried forward. Crew survives with accumulated knowledge.

T15

2011

~9 AD

SGU S2E12 — Twin Destinies

Destiny sent back hours; crew sent back ~2,000 years. Both groups shunted into same new timeline. Current final timeline.

Note: Timeline numbers T1 through T3 are speculative placements based on continuity differences between Origins, the 1994 film, and SG-1. The Cassandra divergence creating T5 is confirmed as a real event but the specific year is unknown. Twin Destinies (T15) is the current end state of the franchise and the presumed starting point of any future Stargate productions.