Polymarket changed the candle convention used to settle its recurring daily Bitcoin Up-or-Down markets by one minute after an October 5 contract produced conflicting price signals between the market’s written resolution rules and a price reportedly displayed to traders.
The discrepancy surfaced in a detailed trader investigation published on October 11, but the underlying rule change is independently visible on Polymarket’s own archived market pages.
The October 5 Bitcoin market instructed traders to compare the closing prices of Binance BTC/USDT one-minute candles closing at 12:00 ET on October 4 and October 5. Polymarket listed $85,256.01 as the price to beat, and the contract ultimately resolved Up.
The distinction sounds trivial until the way Binance labels one-minute candles is considered. A candle that opens at 11:59 ET closes at 12:00 ET, while the candle displayed by Binance as 12:00 opens at noon and closes at 12:01 ET.
Those two candles produced opposite answers on October 5.
The Difference Between 12:00 and 12:01 Changed the Winning Side
The trader investigation says Binance data showed the October 5 candle closing at 12:00 ET at $85,269.78. Against the previous day’s $85,256.01 reference, that represented a $13.77 increase and therefore an Up outcome under the written October 5 rules.
A separate market-data mirror also records $85,269.78 as the final price and the contract as resolving Up.
However, the investigation alleges that a Polymarket page display showed $85,252.00 after the market ended. That price is $4.01 below the previous day’s $85,256.01 reference and therefore visually implied Down.
Crucially, $85,252.00 is also the price Polymarket subsequently used as the starting reference for its October 6 daily Bitcoin market after changing that market to the later candle.
That provides strong evidence that the two numbers were not random data discrepancies. They represented two consecutive Binance one-minute candles: one closing at 12:00 ET and the next closing at 12:01 ET.
The October 5 written contract pointed to the first. The figure reportedly displayed on the page corresponded to the second.
This is exactly the kind of settlement detail that can matter more than a trader’s underlying market view. As Dave Finances noted in its comparison of Polymarket, Kalshi and Robinhood, a prediction-market position is ultimately a trade on the contract’s precise resolution specification, not simply the headline event.
Polymarket Then Rewrote the Next Daily Markets Around 12:01 ET
The strongest part of the story is what happened next.
Polymarket’s October 6 Bitcoin market contains an explicit update saying that the market would use Binance BTC/USDT one-minute candles closing at 12:01 ET on each date.
The clarification goes further, explaining that Binance labels candles by their opening time, meaning the relevant candle appears as 12:00 on Binance even though it closes at 12:01. It explicitly states that the candle opening at 11:59 and closing at 12:00 ET would not be used.
The October 7 Bitcoin market contains the same clarification.
This was not limited to Bitcoin. Polymarket’s October 6 Ethereum daily market received effectively the same rule update, switching its Binance ETH/USDT reference to the one-minute candle closing at 12:01 ET.
That points toward a broader adjustment to Polymarket’s recurring daily crypto-market methodology rather than a one-off wording change to a single Bitcoin contract.
The move is noteworthy as platforms increasingly compete for traders through same-day Bitcoin events and other short-duration contracts where a few seconds or one data point can determine the entire payout.
Post-Close Trading Figures Remain Unverified
The October 11 investigation makes an additional allegation about trading activity during the period of uncertainty.
Its author says Polymarket API data showed approximately $127,500 of Down purchases and $46,000 of Up purchases between the scheduled market end and a subsequent clarification. Those figures have not been independently verified by Dave Finances and should therefore be treated as the researcher’s estimate rather than confirmed Polymarket trading totals.
The author also cautioned that automated trading or wash activity could inflate raw fill figures.
Even without relying on those numbers, however, the underlying issue remains significant. The Oct. 5 market had seven-figure trading volume, and its written rules and a reportedly displayed price could lead a trader to opposite conclusions about which side should win.
That matters as prediction markets increasingly resemble retail trading venues, with active order books, APIs, market makers and traders attempting to exploit small pricing and information differences.
The Rule Change Solved One Problem but Raises Another
There is nothing inherently wrong with Polymarket choosing the 12:01 ET candle rather than the 12:00 ET candle for subsequent markets. Either convention can work if the contract defines it precisely before traders put capital at risk.
The more interesting issue is why the convention changed immediately around a market where the distinction produced opposite outcomes.
There is currently no evidence that Polymarket changed the later rule in order to alter the October 5 outcome. In fact, the October 5 contract ultimately resolved according to its existing 12:00-close language, while the later markets adopted the new 12:01 convention before their respective settlement times.
But the sequence exposes a user-interface problem that prediction markets cannot dismiss as cosmetic.
If the chart, “final price,” price-to-beat display or other prominent interface element points traders toward one candle while the legally operative market text points toward another, sophisticated traders may understand the distinction while casual participants do not.
That creates an information asymmetry at precisely the moment when settlement should become least ambiguous.
A One-Minute Data Convention Is Really an Execution-Risk Issue
For a conventional investor, a $17.78 difference between two consecutive Bitcoin candles is tiny. For a binary prediction contract, it can represent the difference between a position paying $1 and effectively paying zero.
That changes how traders should think about these products.
Prediction-market risk is not just the probability of being wrong about Bitcoin, an election or an economic release. It also includes contract-definition risk, source-data risk, timestamp interpretation, market-interface risk and resolution risk.
Those issues become more important as contract durations shrink. A monthly market can often tolerate small differences between feeds without changing the basic answer. A one-day, one-hour or five-minute market can turn entirely on a single print.
Polymarket could reduce that risk substantially by displaying the exact Binance candle open time, close time, timestamp and final settlement value directly beside the resolution language, rather than expecting users to translate between exchange candle-label conventions themselves.
A permanent, timestamped change log for recurring-market rules would help as well. Traders should be able to see immediately which version of a rule was active when a contract opened and whether any clarification changed interpretation or merely explained wording that was already binding.
Settlement Transparency Matters More as Prediction Markets Grow
The timing is particularly relevant because prediction markets are moving rapidly toward the financial mainstream. The regulatory treatment of prediction markets is becoming a major policy question in the United States, while exchanges are expanding into increasingly short-duration and trading-oriented contracts.
The Commodity Futures Trading Commission describes event contracts as financial products whose value depends on defined outcomes, reinforcing why precise contract terms and settlement mechanisms matter.
Polymarket’s international platform is separate from its CFTC-regulated U.S. business, so the October 5 Bitcoin contract should not be confused with a U.S.-regulated Polymarket contract. But the market-design lesson applies across venues.
As prediction contracts become faster and more liquid, the rulebook increasingly functions like an exchange’s matching-engine specification. A single minute is no longer a footnote when it can reverse the payout.
The October 5 Bitcoin market appears to have resolved according to its written terms. The bigger concern is that traders may have been shown information that pointed toward a different result before that resolution became clear.
Polymarket’s subsequent move to explicitly define the 12:01 ET candle removes much of that ambiguity for the affected later markets. It also leaves an obvious question: whether the platform now needs the same precision in its interface as it has finally added to the rules.
Johan Shamshad is a financial markets writer at Dave Finances covering cryptocurrencies, trading platforms, brokers, fintech, financial regulation, and developments across global markets. He previously worked at Gulf News, adding newsroom experience to his coverage of fast-moving financial and digital-asset markets.
His work focuses on identifying market-moving events, company developments, regulatory changes, product launches, and shifts in trading and financial infrastructure.
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