Fixed vs rolling horizons: when your clock starts at your trade, and when it doesn't

Short answer: A rolling horizon starts at your fill: on Rizon each contract expires a fixed time after its own trade, on the first whole second at least that far on, from 15 seconds to 7 days, so every trader gets the full horizon whenever they arrive. A fixed horizon is one date or result that every contract shares, like an election or the Fed's rate on Dec 31, 2027; a date market is a fixed market whose number is itself a date. Rolling fits numbers with a live feed (Bitcoin, gold, uptime); fixed fits events that happen once.

Every horizon contract on Rizon pays 2× and trades at 50/50 (see What is a horizon contract?). What differs between markets is the clock. This post sets out the three kinds, which market uses which, and why.

The three kinds, side by side#

Every listed market, by horizon#

As decided on Oct 29, 2026 (the app's markets panel is the live list):

How each expiry is computed#

Rolling. Expiry is the first whole second at or after the fill time plus the horizon. A fill at 15:24:41.300 on BTC-1m expires at 15:25:42.000, and fills within the same second share one expiry, so each market has one contract per second, a finite set that makers can net and quote. Bitcoin settles on the last price at or before expiry (a push if there's none in the 5 seconds before it); gold, on its index (a push if no source is fresh within 30 seconds). The uptime markets settle on the uptime over the 7 days after your fill, where downtime counts major outages in full and partial outages at 0.3, as Statuspage computes it.

Fixed. Every contract expires at the market's one moment, and trading stops at its close, or when Rizon halts it because the result is in (the House once every race is called, Anthropic's market cap when the first session closes). A fixed market settles on its result from the named source, not on a timer: a result that arrives before expiry settles every open contract at once, and a market can be voided, with everyone refunded, when its event never happens.

Date. The number is the day the event happens, as a Julian Day Number, and strikes are the midnights between days. A contract at a strike expires at that midnight or the deadline, whichever is first, plus 2 days for the source to report: if the event is reported first, it settles at once on its day; if not, Higher wins. Worked examples are in the US–Iran post.

Why rolling for live numbers#

Up/down venues sell live numbers in blocks on the clock. Polymarket runs Bitcoin windows of 5 minutes, 15 minutes and 4 hours, and gold windows of 15 minutes; Kalshi runs 15-minute Bitcoin (KXBTC15M) and gold (KXGOLD15M) windows. They trade: on Oct 29, 2026, Kalshi's 03:00 ET windows had traded about 2.68M Bitcoin contracts and 291K gold contracts. But everyone in a block shares one start and one price to beat, so whoever arrives late gets less time and a price that has already moved. Across 8,633 five-minute Bitcoin windows, a random arrival found half the window gone and the side ahead already worth a median 74¢ (the data).

A rolling horizon has no blocks. Your contract starts at your fill and runs its full length, at a strike next to the price, so it's 50/50 whenever you trade. That needs a number that can be read at any second, which is why the rolling markets are prices and status pages.

The horizon has to be long enough for the number to move, though. Uptime is almost always 100% over a minute, so its horizon is 7 days. And Elon Musk's post count, which is often still for long stretches, makes a poor rolling number: measured from Sep 28 to Oct 27, 2026, 80% of 15-minute windows and 55% of hour-long windows had no new post, so while he's quiet, Lower at the count plus a half-post is the favourite and nobody can sell it at 2×. Rizon built rolling Elon markets (15 minutes, 1 hour, 6 hours) and keeps them unlisted; the listed one is weekly and fixed, on Polymarket's own window.

Why fixed for events#

An election, a Fed decision or an IPO happens once, and its number is only known at the end, so every contract has to share the result. What a fixed horizon keeps from the event markets is the date; what it changes is the quote. Instead of 10 or 30 bucket markets, each with its own book, there's one book of strikes on the number, at 50/50. Bucket markets vs one book shows the difference on the Fed, and the midterms post on seat counts.

When the question is when something happens, the number is the date, and the market is a date market. The deadline caps it: if nothing happens by then, Higher wins at every strike.

FAQ#

What is a rolling horizon?#

An expiry measured from your own trade: on Rizon each contract expires a fixed time after its fill (15 seconds to 7 days), on the next whole second, so every trader gets the same full horizon.

What is a fixed horizon?#

One expiry for every contract in a market, tied to a date or a result, like an election or the Fed's rate on Dec 31, 2027. Fixed markets settle when the result is known, from a named source.

How is a fixed horizon different from a fixed window?#

A fixed window is a block on the clock that restarts every few minutes, so most traders arrive partway through it. A fixed horizon belongs to a market that resolves once, on an event, and the strike still moves to 50/50 in the book.

Why isn't Elon Musk's post count a rolling market on Rizon?#

Because over short horizons it's often unchanged: from Sep 28 to Oct 27, 2026, 80% of 15-minute windows had no new post, so the book would be one-sided. Rizon lists a weekly fixed market on XTracker's Friday-to-Friday count instead.

What happens to a date market if the event never happens?#

At the deadline the number becomes the deadline's day, so Higher wins at every strike.