Does Monday produce better returns than Friday? What about shorting volatility overnight? The Weekday Backtester answers these questions with real data going back over a decade.
"Is there a best day of the week to buy stocks? What if I only held positions from Monday to Friday and sat out the rest?"
Day-of-week effects are one of the oldest ideas in market research. Academic papers have studied them for decades, but actually testing them on your own tickers has always required downloading data, writing scripts, and building your own analysis. Until now.
We built a tool that lets you test weekday timing strategies on any equity in seconds.
The Weekday Backtester (Long) tests long entries on equities like SPY, QQQ, AAPL, NVDA, and TSLA. Pick a day to buy, a day to sell, and see the full historical performance going back over a decade.
Pick a buy day and a sell day. The strategy buys at the buy day's open and sells at the sell day's close, one trade per week. Buy Monday open, sell Friday close tests the classic "hold for the week" approach. Buy Wednesday, sell Thursday tests a shorter window. Every pair produces different results, and the tool lets you compare them all.
Pick a single day. The strategy buys at the open and sells at the close on that day only. This isolates each weekday's intraday return. Is Monday's open-to-close historically better than Wednesday's? Are Fridays consistently weak? The data will tell you.
Buy at a day's close and sell at the next trading day's open. This captures only the overnight gap. Equity markets tend to move differently during overnight sessions than during regular hours. Friday overnight is especially interesting because it spans the full weekend, buying Friday's close and selling Monday's open.
Hover over any day button in Overnight mode to see the exact trade description.
The Find Best Combination button tests every possible day pair (20 combinations in Multi-Day, 5 days in Intraday and Overnight) and surfaces the one with the highest annualized return. The buttons update to show the winning combination, and the full results render below.
Timing matters even for long-term investors. If you dollar-cost average into SPY every week, does it matter whether you buy on Monday or Wednesday? If you sell covered calls, should you enter on a specific day? The historical data shows that some days consistently outperform others, even if the edge is small.
The overnight mode reveals something most traders never see: the gap between yesterday's close and today's open. In equities, overnight returns have historically accounted for a large portion of total market returns. This tool lets you see that pattern on any ticker.
This won't replace a trading strategy. But it can refine your timing within one.
Test which day of the week produces the best returns on any ticker. Three strategy modes, full equity curves, and trade logs.
Open the Tool
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