If parallel universes are included as alternate timelines, how many alternate Star Trek timelines have been presented to us onscreen in the Franchise? For the sake of clarification, Tomorrow is Yesterday represents 3 timelines to me.

  • Timeline 1- Beginning of episode until Christopher's & the Air Policemen's (although, technically, I suppose each persons beam back could constitute a new timeline) beam back.

  • Timeline 2- Post beam backs until the Enterprise is slingshoted out of the 1960's.

  • Timeline 3- When Star Fleet contacts the newly returned Enterprise in what Spock hopes to be the Enterprise's original pre-1960's timeline.

So, due to the murky nature of timey whiminess illustrated by the possibility of of a 4th Air Policeman timeline, I understand there can't and won't be a hardline perfect answer to this question. What I'm hoping for is an acceptable general ball park figure.

(And, if the voters deem this Franchise wide question too broad, I'll narrow it down to TOS, but the Franchise wide answer was what brought this question to mind.)

1 Answer 1


It depends on if you consider alternate dimensions alternate timelines, Mirror, Mirror is described as an alternate dimension, but it is presented often as an alternate timeline. With that in mind you have:

  • The Naked Time TOS:s1e06 - created a timeline with 2 co-existent Enterprises for 3 days.
  • The Alternative Factor TOS:s1e20 - If you consider an alternate universe where anti-matter became the dominate baryonic matter an alternate timeline then one is introduced.
  • Mirror, Mirror TOS:s2e10 - First introduction of the alternate universe/timeline of the Terran Empire that is revisited in Ent:s4e18, Ent:s4e19, DS9:s2e23, DS9:s3e19, DS9:s4e20, DS9:s6e08, and DS9:s7e12
  • City on the Edge of Forever TOS:s1e28 - A second timeline is created when McCoy saves Edith Keeler
  • Assignment Earth TOS:s2e26 - May or may not have spawned a second timeline, episode unclear.
  • Tholian Web TOS:s3x09 - Though not directly spawning a timeline, references in Ent:s4e18 as source of USS Defiant.
  • All our Yesterdays TOS:s3e23 - May have spawned mutliple timelines, but effects of time travel localized to Beta Niobe system.
  • Yesteryear TAS:s1e02 - Guardian of Forever episode that changes Spocks past spawning a timeline where an Andorian is second in command of Enterpirse
  • Star Trek IV - We see a timeline where the crew does not make the trip or returns to 2286 briefly.
  • We'll Always Have Paris TNG:s01e24 - Data coordinates with divergent timeline versions of himself, and the rest of the crew encounters themselves. Unsure if this was just localized or spawned actual timelines.
  • Time Squared TNG:s2e13 - Picard creates a closed loop timeline where he abandons the Enterprise, may be localized event or may cause destruction of Enterprise in other timelines.
  • Yesterdays Enterprise TNG:s3e15 - A timeline where the Enterprise-C was not destoyed rescuing a Klingon colony. As well as what would become the main show timeline, a timeline where Tasha Yar was captured by Romulans in 2344. Show timeline now includes Sela (s4e24, s4e26, s5e01, and s5e08)
  • A Matter of Time TNG:s5e09 - It is unknown what effects Berlinghoff Rasmussen had on the timeline.
  • Times Arrow TNG:s5e26 and s6e01 - Guinan implies that she is aware of a timeline where she and Picard do not meet. Seeing as she was able to sense the alternate timeline in Yesterday's Enterprise this does seem likely.
  • Tapestry TNG:s6e15 - Unknown how localized Q's meddling in Picards history was.
  • Cause and Effect TNG:s5e18 - Another closed loop, that ends with the USS Bozeman rejoining the timeline.

However in TNG:s7e11 Parallels you have multiple Worf's jumping between multiple adjacent timelines. And as the episode progresses the multiple timelines intersect causing multiple Enterprises to manifest. During this event over 285,000 Enterprises responded to a hail and we can assume that there were many more manifested before the rift was sealed. At this point I stop counting because of the introduction of uncountable timelines.

Memory Alpha has good resources on the Time Travel episodes and the Parallel Universe Episodes pages if you want to dig deeper.

  • Cause and Effect: TOS - Technically it's a time loop, but since things change each time through eventually culminating in loop release, you could argue that each one is a separate timeline.
    – JohnP
    Commented Aug 21, 2014 at 22:20
  • Whoops, skipped that one, and should probably pull Firstborn since it takes place after Parallels. Even though it does feed into the "Everything sucks for Worf" theme. Commented Aug 21, 2014 at 22:27
  • True, but at least he got to shack up with Troi for a while. That's worth a fair amount of suckitude. </> Oh, and it's hard to tell how many loops the Enterprise went through in CandE, since they were in the loop for 17.4 days, and went through 4 just on the show. I suppose you could argue that each loop was 12 hours since it is one duty day, so 35ish loops.
    – JohnP
    Commented Aug 21, 2014 at 22:36
  • Eh, his wives keep dying, he never feels comfortable with Alexander, an outsider in both Federation and Kligon Empire. In every view of the future with him in it his failure as a diplomat leads to a period of cold war or limited conflict between the Federation and Klingon empire. Though he is supposed to be total badass spends most of Next Gen being owned. Commented Aug 21, 2014 at 22:40
  • You are missing All Good Things the series finale of TNG! Count at least that! :)
    – Lexible
    Commented Aug 21, 2014 at 23:38

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