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Research

What the calendar does to returns

Every claim here is measured against real price history, and every number is one you can check yourself.

Seasonality

The Santa Claus Rally: what the data actually shows

The Santa Claus Rally is a real, narrowly defined seven-day window — not the whole of December. Here is what it has returned, how often, and why the average misleads.

August 9, 2026 · 8 min read

Sell in May and Go Away: does the six-month rule still work?

The May-to-October window really has underperformed November-to-April for a century. Whether that gap is worth trading is a different question, and the answer is mostly no.

August 9, 2026 · 9 min read

The worst month for stocks, and why September keeps winning that title

September has the weakest average return of any month across a century of US equity history. What is less often said is how thin the evidence for a cause is.

August 9, 2026 · 7 min read

Timing

The best time of day to buy stocks, and the cost of the opening bell

The trading day has a repeating shape: two volume peaks and a quiet middle. Knowing it will not predict direction, but it will stop you paying a wider spread for nothing.

August 9, 2026 · 7 min read

When is the best time to buy stocks? Three timeframes, three answers

The question hides three different questions — time of day, day of week, and month of year. Two have small real effects and one has almost none.

August 9, 2026 · 9 min read

When to sell a stock: the four rules that actually decide it

Most selling decisions are made emotionally and justified afterwards. These four rules are decided in advance, which is the only property that matters.

August 9, 2026 · 10 min read

Backtesting

How to backtest a seasonal pattern without fooling yourself

Most seasonal backtests are wrong in the same four ways. Here is the method that survives contact with real money, and the three numbers to report instead of the average.

August 9, 2026 · 11 min read