Bitcoin has long treated September as its cruelest month, but the pattern failed again this year: the asset closed its fourth consecutive September in positive territory.
According to CoinGlass data, Bitcoin gained 6.33% in September, extending a streak that includes a 3.91% rise in 2023, a 7.29% advance in 2024 and a 5.16% gain in 2025. The four straight positive Septembers follow six consecutive losses between 2017 and 2022. Since 2013, the month has averaged a decline of roughly 2.4%, based on CoinGlass figures.

The run drew attention across the industry. DeFi app highlighted it in a post on X. "For years, 'Red September' was a rule in crypto," it wrote, adding that the market now "trades on fundamentals, revenue, and real usage, not folklore."

The claim raises two questions: which of Bitcoin's long-standing rules are breaking down, and what should market participants watch instead?

More Than a September Problem

"Uptober," the notion that October reliably delivers gains, also fell short last year. October turned negative for the first time since 2018, and the fourth quarter then dropped 23.07% — despite an average fourth-quarter return of more than 77% in historical data.

Another seasonal rule has eroded as well. Before 2026, every green August in CoinGlass data going back to 2013 had been followed by a negative September. This year, August's 24.95% surge was followed by another 6.33% rise in September. July, August and September all finished higher for the first time in that dataset, producing a 42.71% gain for the third quarter.

The moves do not mean seasonal trends have disappeared. They do show why calendar-based patterns, which are drawn from historical averages rather than forward-looking fundamentals, have become harder to use as standalone signals.

Is the Four-Year Cycle Dead?

The bigger test concerns the four-year halving cycle — the idea that Bitcoin moves through roughly four-year phases around halving events, when the reward for mining new Bitcoin is cut in half.

The current cycle has behaved differently. Bitcoin peaked in October 2025, roughly 18 months after the April 2024 halving, in line with the timing of earlier cycles, but the decline that followed was shallower than in previous cycles.

Some analysts believe the old cycle has broken down. In its 2026 crypto outlook, trading firm Wintermute declared that the "four-year cycle is dead," arguing that structural factors such as exchange-traded funds (ETFs), digital asset treasuries — companies that hold Bitcoin on their balance sheets — and the movement of capital now matter more than timing.

Bitwise Chief Investment Officer Matt Hougan has made a similar case, saying the forces behind the cycle — including the halving, interest-rate cycles and leverage — have weakened.

Others disagree. Galaxy Research argued in June that the cycle remains visible in the data, even as the swings shrink, with each successive cycle producing a smaller peak-to-trough decline.

The debate is less about whether Bitcoin has changed and more about how much the old cycle still explains. Many observers are watching where money is moving and how financial conditions are shifting instead.

US spot Bitcoin ETFs took in about $3.08 billion over nine straight days through Sept. 29. The streak ended the following day with an outflow of roughly $148.69 million. Because these products report their flows daily, the figures have become one of the most closely watched gauges of institutional demand.

Bernstein analysts have pointed to a changing ownership structure. In June, they said combined flows from ETFs and corporate treasury companies had brought about $12 billion of net new capital into Bitcoin in 2026 so far, against roughly $60 billion during 2025. In August, they linked Bitcoin's rebound toward $80,000 to improving liquidity, renewed ETF demand and larger US Treasury purchases of longer-dated debt.

That relationship is being tested again. The 10-year Treasury yield — a benchmark for US borrowing costs and a widely watched gauge of financial conditions — reached 5.223% on Sept. 24, a level not seen since June 2007, and it hit 5.23% on Sept. 25, its highest since 2007. On Oct. 1, the 10-year climbed to 5.34%, its highest level since 2002.

With calendar rules losing their grip, daily ETF flow reports and Treasury yield moves now offer the most direct, regularly published readouts of the two forces analysts cite most: where money is moving and how financial conditions are shifting.