Silo Timeline Explained: From the Before Times to Silo 18 and Silo 1

Spoiler warning: this article covers confirmed events through the end of Silo Season 3, including the finale’s reveals about Silo 1. If you haven’t finished Season 3, stop here.

Silo unfolds in two periods that the show deliberately keeps apart for as long as possible: the Before Times, when the silo project was built, and the underground present, centuries later, where Juliette Nichols lives. Season 3 is what finally connects them — not just thematically, but literally, revealing that the man who once opposed the project in the Before Times is the same person running Silo 1’s operations in Juliette’s era. Below is that timeline in order, using what the show has actually confirmed and flagging the points where exact dates remain deliberately unclear.

Silo Timeline at a Glance

Era	Key Events	Status of Date
Before Times	Daniel Keene, Helen Drew, Per Stensen’s project begins	Implied real-world-adjacent period, no exact year confirmed
Founding	The silo network is built	Confirmed: 352 years before Juliette’s present (per Bernard, Season 2)
Last rebellion / reset	Salvador Quinn wipes Silo 18’s memory	Confirmed: 140 years before Juliette’s present
Generations underground	Ordinary silo society, restricted history	No exact span given; implied multiple generations
Silo 17 collapses	Rebellion, Solo left alone	Confirmed: roughly 30+ years before Juliette’s present
Silo 18 pre-Juliette	George Wilkins, Allison and Holston Becker	Immediately before Season 1
Juliette’s era	Seasons 1 through 3	The show’s present day

The Before Times

Season 3’s past-set storyline centers on Congressman Daniel Keene and journalist Helen Drew, uncovering a conspiracy tied to a dirty bomb and, eventually, to billionaire Per Stensen’s silo project. A visual clue from Season 2 — a VR recording of the “Monteverde Cloud Forest Biological Reserve, 2018” — suggests the Before Times track roughly with the real world’s own recent history, though the show has never stated an exact calendar year for any of it. Our Troy/Daniel Keene explainer covers who Daniel was during this period in more depth; this section is only about where it sits on the timeline.

How the Silo Project Began

Season 3 establishes that Stensen’s silos were already under construction before any apocalypse actually happened — built as insurance against a threat he believed was coming, centered on nanotechnology weapons (the “gray goo” of the season’s eighth episode) rather than a disaster that had already occurred. The show puts the network at 51 silos, with Silo 1 built to oversee the rest. Our Silo 1 explainer covers what that oversight role actually involves; the timeline point that matters here is that Silo 1’s authority over the network was designed in from the start, not something it acquired later.

When People Entered the Silos

The show has not given an exact year for when people actually moved underground. What’s confirmed instead is a distance from the present: Bernard Holland tells Lukas Kyle in Season 2 that the silos were built 352 years before Juliette’s current timeline. Combined with the Before Times’ apparent real-world-adjacent setting, that points to a founding sometime in the early-to-mid 21st century and a present-day setting roughly in the 24th century — but the show itself has not confirmed a specific year for either end of that span. Treat “352 years” as the one solid figure, and treat any exact calendar year built on top of it as an estimate, not canon.

The Early Years of Silo 1

Once the network was operating, Silo 1 functioned differently from every other silo from the beginning — its operators cycled through cryogenic stasis rather than living out a single continuous lifetime, extending their working lives across generations. Daniel Keene’s path into that system, and what it turns him into as Troy, is covered in full in our Troy explainer. For the timeline, the important point is that Daniel’s individual cycles of wake-and-resuppress happen across the same centuries that pass for everyone else in the ordinary silos — he’s not aging through that time the way Silo 18’s residents are.

Generations of Life Underground

For most of the 352 years between founding and Juliette’s present, the show doesn’t track specific dates — only the broad fact that ordinary silos like Silo 18 became closed societies, governed by the Pact and kept ignorant of their own history through controlled information and, at least once, a deliberate mass memory wipe. That wipe is the other confirmed fixed point on the timeline: Salvador Quinn, serving as Silo 18’s Head of IT, introduced a memory-suppressing compound into the water supply 140 years before Juliette’s present, following a rebellion, and destroyed the physical evidence of what came before. Everything Silo 18’s residents “know” about their own history, going into Season 1, dates from after that reset.

What Happened to Silo 17?

Silo 17’s rebellion and collapse predates Juliette’s arrival there by a generation. Steve Zahn’s Solo — real name Jimmy — was a child, around 11 or 12, when the uprising happened; by the time Juliette finds him, decades of isolation have visibly aged him well past that. Characters born after the rebellion, including their parents, weren’t alive for it, which is how the show signals roughly three decades or more between Silo 17’s fall and Juliette’s discovery of it, without ever stating an exact figure. What triggered Silo 1’s response there, and how directly the Safeguard was involved, is not spelled out in full — the show leaves Silo 17’s exact fate more ambiguous than Silo 18’s.

Silo 18 Before Juliette

Immediately before Season 1 opens, Silo 18 is already showing cracks in its official story. George Wilkins requests a transfer to Mechanical and finds the cavern and digging machine beneath the silo; not long after, he’s found dead — ruled a fall, but suspected by Juliette to be murder. Around the same time, Sheriff Holston Becker’s wife, Allison, asks to go outside and is sent to clean, having uncovered evidence that other silos exist. Holston follows her out himself not long after, naming Juliette his successor before he goes. That sequence — Wilkins’ death, Allison’s cleaning, Holston’s cleaning — happens within roughly the same year, immediately setting up Juliette’s rise to sheriff.

Juliette Nichols Breaks the Cycle

Juliette becomes sheriff by inheritance rather than ambition, and spends Season 1 investigating Wilkins’ death, uncovering the hard drive that proves other silos exist, and eventually being sent to clean herself. She survives — the first confirmed instance of that happening — because her visor is quietly sabotaged to let her see the truth about the outside world instead of a projected illusion. From there she finds Silo 17, encounters Solo, and eventually makes her way back to Silo 18, carrying knowledge no sheriff before her had.

Silo 18’s Rebellion

Juliette’s return doesn’t resolve things quietly. Bernard Holland, Camille Sims and the Algorithm behind Silo 18’s chain of command spend Season 2 and the first half of Season 3 trying to contain what Juliette knows, while Mechanical’s workers and Juliette’s allies push back. That conflict is what eventually exposes the Safeguard directly and pulls Silo 1 into the open. Our full Season 3 ending explainer covers exactly how that rebellion plays out and resolves — this timeline is only tracking where it sits in sequence.

Season 3 Connects the Two Timelines

The structural trick of Season 3 is that the Before Times stop being flashbacks and become the direct origin of Juliette’s present conflict. Daniel Keene, swept into Silo 1 during the same catastrophe that separates him from Helen, becomes Troy — the same operator Victor wakes centuries later to handle Silo 17’s rebellion and, later, Silo 18’s. The chain runs Daniel Keene into Troy into Silo 1’s operational structure into the Project’s control over every other silo, arriving directly at Juliette’s fight to keep Silo 18 alive. It’s not a parallel story anymore by the finale — it’s one story told from two ends.

Where the Timeline Stands After Season 3

At the close of Season 3, Silo 18 has survived Silo 1’s attempt to activate the Safeguard, Victor is dead, and Juliette knows Silo 1 can simply try again. Troy has been given Helen’s name for the first time since his memory was suppressed, and the conflict has shifted from Juliette fighting for control inside her own silo to Juliette and her allies preparing to reach Silo 1 directly. Nothing beyond that point is confirmed — our Season 4 guide tracks what’s actually known about the final season as it’s announced.

How Much Time Has Actually Passed in Silo?

Apple has not stated an exact number of years for how long humanity has lived underground as a single confirmed figure — what exists instead is Bernard’s “352 years” line anchoring the founding, and the separate “140 years” figure anchoring Silo 18’s last rebellion and memory wipe. Those are two different reference points, not conflicting claims: roughly two centuries pass between the silos being built and Quinn’s reset, and then another 140 years pass between that reset and Juliette’s present. Anything more precise than that — an exact founding year, an exact current year — is a fan calculation built on top of those two figures, not something the show has stated directly.

TV Timeline vs. Book Timeline

Hugh Howey’s source trilogy — Wool, Shift and Dust — uses its own explicit dates: construction completing around 2052, with the present-day story set around 2345. Apple’s adaptation has not adopted those exact years on screen, and Bernard’s “352 years” line doesn’t map cleanly onto them, which suggests the show is telling an adjacent but not identical chronology rather than a direct port of the books’ calendar. The bigger structural difference is what each version reveals when: the show holds back Silo 1’s full role and the Before Times’ connection to the present until Season 3, using it as a mid-series reveal rather than background the audience has going in. Treat any date sourced purely to the books as book-only unless the show has separately confirmed it. Our full comparison of Season 3 against Shift covers how much further the two versions diverge beyond just dates.

Silo Timeline — The Short Version

1. The Before Times: Daniel Keene, Helen Drew and Per Stensen’s project take shape.
2. The 51-silo network is built — 352 years before Juliette’s present.
3. Silo 1 begins overseeing the network, with operators cycled through cryosleep.
4. Generations pass underground under the Pact, with history tightly controlled.
5. Silo 18 has a rebellion; Salvador Quinn wipes its memory — 140 years before Juliette’s present.
6. Silo 17 collapses in its own rebellion, leaving Solo alone for three decades or more.
7. George Wilkins, then Allison and Holston Becker, die or leave within the same year, just before Season 1.
8. Juliette becomes sheriff, survives cleaning, and finds Silo 17.
9. Silo 18 moves toward open rebellion against Bernard, Camille and the Algorithm.
10. Season 3 reveals Daniel Keene became Troy, and connects the Before Times directly to Silo 1’s present-day control.
11. Season 3 ends with Silo 18 surviving the Safeguard and turning its attention to Silo 1 itself.