Calendar · daily rule · Indexes & ETFs
Lunar Cycle on S&P 500 ETF
What the play says
Latest reading: Days −13.00
SPY with the play, last two years
Shading shows the play's call from the close that triggered it.
Days from the nearest full moon
Dashed lines at −7, 7.
Growth of $10,000 since 2005
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding SPY over exactly the same dates, after costs.
| Play, since 2005 | Hold, since 2005 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | +5.3% | +11.0% | +6.8% | +13.9% |
| Total return | +209% | +861% | +39% | +91% |
| Worst drawdown | −38.0% | −55.2% | −19.2% | −24.5% |
| Volatility | 12.6% | 18.9% | 11.6% | 17.1% |
| Sharpe ratio | 0.33 | 0.55 | 0.30 | 0.62 |
| Time invested | 49% | 100% | ||
| Switches per year | 24.7 | 0 |
Every call, graded
Right on 272 of 541 closed calls (50%). In calls averaged +0.5%; out calls saw SPY move +0.5% on average.
| Called | Call | Price | Until | SPY moved | Result |
|---|---|---|---|---|---|
| Oct 2, 2026 | IN | $769.64 | now | +1.1% | open |
| Sep 18, 2026 | OUT | $761.69 | Oct 2, 2026 | +1.0% | ✕ wrong |
| Sep 4, 2026 | IN | $768.28 | Sep 18, 2026 | −0.9% | ✕ wrong |
| Aug 20, 2026 | OUT | $760.71 | Sep 4, 2026 | +1.0% | ✕ wrong |
| Aug 5, 2026 | IN | $767.88 | Aug 20, 2026 | −0.9% | ✕ wrong |
| Jul 21, 2026 | OUT | $746.43 | Aug 5, 2026 | +2.9% | ✕ wrong |
| Jul 6, 2026 | IN | $749.42 | Jul 21, 2026 | −0.4% | ✕ wrong |
| Jun 18, 2026 | OUT | $744.89 | Jul 6, 2026 | +0.6% | ✕ wrong |
| Jun 5, 2026 | IN | $733.83 | Jun 18, 2026 | +1.5% | ✓ right |
| May 22, 2026 | OUT | $741.88 | Jun 5, 2026 | −1.1% | ✓ right |
| May 8, 2026 | IN | $733.90 | May 22, 2026 | +1.1% | ✓ right |
| Apr 23, 2026 | OUT | $704.88 | May 8, 2026 | +4.1% | ✕ wrong |
An in call is right when the price rose before the next call; an out call is right when it fell. The latest 12 of 542 calls shown.
How the play works
- The full-moon period is the day of the full moon plus the 7 calendar days before and after it, using U.S. Naval Observatory dates.
- Out for any session that falls in a full-moon period.
- In for the rest of the lunar month (the new-moon period).
The paper went long in new-moon periods and short in full-moon periods. Be The Puck holds T-bills instead of shorting.
Session dates are compared with the full-moon date in universal time (GMT) with no time-zone shift, as in the paper.
Dichev and Janes (2003) found a similar new-moon advantage in U.S. indexes back to 1896. The 15-day definition here follows Yuan, Zheng and Zhu.
Moon dates on file run from 1990 to 2030; earlier history gets no call.
Where the rules come from
The case against
Valeriy Zakamulin tested moving-average timing on up to 155 years of U.S. stock data and found no statistically significant edge in the second half of that record. The rules earned their keep in a few severe bear markets and lagged buy and hold for long stretches in between.