Timestamps
Polymarket Timestamps Explained
Every row in the Polymarket archive is a timestamped fact, and the timestamp rules decide what can be joined: capture at the 250ms UTC bucket, events at their true second, settlement at its fixed second. This page documents the clock.
Figures measured as of 2026-09-24 on the published PolyOrderbooks archive.
Types
The three timestamps
Rules
Joining by time without drift
The join rule is one clock: books, prices, and metrics bucket to the same UTC integer; the tape joins on its true second; and the resolve second is a column, not an inference. Cross-venue studies should bucket Polymarket against the other venue's own timestamps on the UTC second — that is the correlation standard.
The trap is display time: a front-end that shows "14:42:50" while the row stores a different UTC second is a classic drift source; the schema keeps the stored second canonical.
Worked
Same-second alignment, survived
The same-second repricing incident — ETH 0.815 to 0.065 within one printed second on Binance — is reconstructable because the reference second, the tape second, and the 250ms book buckets all share the UTC grid; any coarser timestamp would blur the event into a trend.
The lesson generalizes: the resolution of your timestamps caps the resolution of your claims.
Honest
The honest framing
Timestamps are the one field that cannot be audited from prose — the honest text says time is UTC seconds on the archive's grid, precisely so any study can re-verify the instant it cites.
FAQ
What timezone do timestamps use?
UTC unix seconds; frames bucket at the 250ms grid, events at their true second, resolution at its fixed second.
How do I join books and tape?
On the same UTC clock — books bucket to the 250ms grid and the tape joins by its true second.
Why does second-level timing matter?
The 26-second family collapse and same-second reprices only exist in a record that keeps the second — coarser stamps blur events into trends.