📘 How to Use This Information

📊 What the Numbers Mean

• Average Return: The average percentage change for that weekday over 10 years.
• Positive Days: How often that day ended with a gain rather than a loss.
• Green = Better, Red = Worse: Bars are colored from red to green based on performance.

📐 How the Weekday Pattern Math Works – Simplified

📅 Daily Return Calculation

1. Take today’s closing price and divide by yesterday’s closing price
2. Subtract 1 from this number
3. Multiply by 100 to get percentage return

Example: If a stock closed at $105 today and $100 yesterday:
(105 ÷ 100) – 1 = 0.05 → 0.05 × 100 = 5% daily return

📆 Weekday Analysis

1. Group all returns by weekday (all Mondays together, all Tuesdays, etc.)
2. For each group, calculate:
   • Average Return: Sum of all returns ÷ number of days
   • Percentage of Positive Days: Days with gains ÷ total days

🚫 Removing Outliers

1. Measure how far each return is from the average (in standard deviations)
2. Remove returns more than 3 standard deviations from the mean
3. This filters extreme events like crashes or spikes

🎨 Color Mapping

1. Identify the highest and lowest average weekday returns
2. Create a red-to-green gradient scale
3. Map each weekday onto that scale for intuitive visual insights

📊 This structured method ensures results are statistically valid and visually meaningful across thousands of trading days, offering real-world insights into subtle but persistent weekday effects.

📈 Why These Small Differences Matter

Weekday-based return differences may look small (often less than 0.2%), but their impact can be significant when combined with consistency and time:

• 📈 Compounding Effect: Small advantages add up dramatically over years of investing.
• 🔁 Consistency: A pattern that repeats every week can present ongoing opportunities.
• 🛡️ Risk Reduction: Knowing which days tend to be weaker can help you better manage volatility.

📊 Statistical Interpretation

The key insight from this analysis is that even small differences in average returns can be statistically significant when:

• The sample size is large (thousands of trading days)
• The pattern is consistent across multiple markets
• The effect persists over long time periods

This is based on the Central Limit Theorem, which states that with a large enough sample size, the sampling distribution of the mean approaches a normal distribution regardless of the population’s distribution.

By compounding these small percentage differences over many years, the cumulative effect on investment returns can be substantial. For example, a 0.1% advantage, compounded weekly over a 10-year period, would yield approximately 5% more total return compared to a random day strategy.

This is the mathematical basis for why the weekday effect, while small in daily terms, can be meaningful for long-term investment strategies.

🛠️ Practical Ways to Apply This Knowledge

If you’re a regular investor who makes monthly contributions to savings or investments:

✅ DO

• Schedule Regular Investments: Consider setting up your automatic investments to happen on historically stronger days.
• Plan Monthly Contributions: If you invest monthly in index funds or ETFs, choosing better-performing weekdays could improve long-term results.
• Be Consistent: The real power comes from applying this pattern consistently over many years.

❌ DON’T

• Don’t Use for Short-Term Trading: These are long-term patterns, not day-trading signals.
• Don’t Expect Guarantees: Past patterns don’t guarantee future results.
• Don’t Invest Based Only on Weekday: This should be just one small factor in your investment decisions.

💬 Final Thought: Smart investing is about consistent, small improvements over time. Choosing a statistically better weekday for your regular investments is a simple tweak that could boost your long-term returns without requiring any additional money or risk.