Bitcoin 500-Day Rule

Bitcoin cuts the miner block reward in half every 210,000 blocks — roughly every four years. The Bitcoin 500-day rule is the fixed-window framing of that event: buy at T-500, exactly 500 days before the halving, and sell at T+500, exactly 500 days after it. BTC500 does not try to pick the exact bottom or top of that cycle. It measures one fixed window around the event and shows what historically happened inside it.

T-500 is the calendar day 500 days before a halving. T+500 is the calendar day 500 days after it. The window is about 1,000 days long. Cycles are compared by lining those two dates up across the 2012, 2016, 2020, and 2024 halvings, using the same daily price archive as the simulator.

The 500-day span is a simple, auditable rule — not an optimized curve-fit. It is long enough to include the pre-halving stretch and most of the historical post-halving advance, and short enough to leave the later drawdown outside the window. Other windows exist. This one is published so it can be checked.

Historical performance is not a guarantee of future results. Four halvings is a small sample. Later cycles have produced smaller multiples as Bitcoin matured. The next window can be better, worse, or fail.

4 completed windows in this archive finished higher at T+500 than at T-500. The simple average of those window returns is +1959%. That average is a description of a small sample, not a forecast.

The largest completed multiple was the 2016 Halving (+3318%). The smallest was the 2024 Halving (+560%). After the earliest windows, later cycles started at a higher Bitcoin price and the same rule produced a smaller multiple.

The move from T-500 to the halving date was not uniformly positive. The table above is the record; it is not an argument that the next pre-halving stretch must rise.

Between T+500 and the next T-500 the rule is in cash. That gap historically covered the 2018 and 2022 drawdowns. It also means the rule did not own Bitcoin in those stretches. Compare the same dates against buy-and-hold in the simulator before treating the cash window as an advantage.

In all 4 windows with a T-500 print in the archive, Bitcoin closed below the entry price at least one day before the halving. The deepest was the 2012 Halving: $14.07 at T-500, then a low close of $2.30 on Nov 22, 2011 — -83.7% from entry, 128 days later.

Across those windows the median lowest close was -11.7% below the T-500 price, and it arrived 85 days after the buy. Before the halving, a holder sat below the entry price on a median of 74 daily closes — the 2012 window is the extreme case, with almost the whole pre-halving stretch underwater.

These are daily closes, so intraday lows were deeper than any number here. Where a window would start before the price archive does, the first available close is used as its entry. Four cycles is a small sample: the next window can trade below entry for longer, or not at all. A drawdown table is a description of the past, not a forecast and not advice.

The rule fixes one entry date, so the fair challenge is whether that date carries the result. This test keeps the T+500 exit where the rule puts it and moves only the entry — from 120 days earlier to 120 days later — then compares each completed-window multiple with the multiple from entering on T-500 itself.

Every earlier entry in this archive did worse. In the 3 windows where the archive reaches back 120 days before T-500, a T-620 entry (120 days early) produced a smaller multiple in all 3 — median -32.5%, worst -45.1% in the 2020 Halving. Thirty days early pointed the same way: 3 of 3 windows lower, median -12.5%.

Entering late was close to a coin flip for the first two months. A T-530 entry (30 days after the signal) changed the multiple by -4.0% to +19.5% — higher in 2 of 4 windows, median +3.9%. By 120 days late the median was -14.4%, lower in 3 of 4. Part of that is arithmetic: the exit stays fixed, so a later entry holds Bitcoin for fewer days.

The exception is the 2012 window, where entering 120 days late would have produced +356.8% more than the exact date. The archive begins on that window's T-500 itself (17 July 2011), so there is no earlier print to test, and the months after that entry included a fall from $14.07 to $2.30. That is the honest shape of this test: the date is not a knife-edge, but whether a nearby date beat it depended on what price did next — which no calendar could know in advance.

This test covers 4 completed windows, uses daily closes only, and ignores fees and taxes. A different four years could invert the pattern. It is a description of the past, not a forecast and not advice.

BTC500’s historical entry is T-500 — 500 days before the next estimated halving. The live date for the current cycle is November 28, 2026. It will move if blocks run faster or slower than ten minutes.

That date is a rule, not a claim that it is the best day, the cheapest day, or the right day for a given person. Some investors buy earlier. Some wait until after the event. The timing test above shows what missing T-500 by up to four months did in each completed window. The point of publishing T-500 is that it can be backtested — open the simulator on a $500 or $1,000 starting amount to see what that rule did.

BTC500’s historical exit is T+500. For the current estimated halving that date is August 24, 2029. The rule does not sell before the halving and does not trail a moving average. It uses one calendar date.

T+500 is not a forecast of the cycle top. In some completed windows price was still advancing at that point; in others the strongest months were already behind it. Selling then also means sitting out until the next T-500. That is a tradeoff, not a guarantee. Nothing on this site is financial advice.