Best Day of the Year to Invest in COST (Costco)
Based on 41 years of data (1986–2026), October 8 has historically been the best day to invest in COST. Buying on that date and holding for ≈ 1 month returned an average of +5.59% with a 82% win rate. The weakest day is March 30 (-2.85%).
Seasonal Return by Day of Year for COST
Each point is the average return over the following ≈ 1 month (21 trading days) if you had invested on that calendar date. Cyan = best day, red = worst day.
10 Best Days to Invest in COST
| Date | Avg Return (≈ 1 month) | Win Rate | Samples |
|---|---|---|---|
| October 8Best | +5.59% | 82% | 28 |
| October 26 | +5.40% | 82% | 28 |
| October 27 | +5.14% | 76% | 29 |
| May 25 | +5.03% | 73% | 22 |
| October 29 | +4.99% | 85% | 27 |
| November 1 | +4.81% | 71% | 28 |
| October 9 | +4.79% | 76% | 29 |
| November 2 | +4.72% | 82% | 28 |
| October 28 | +4.44% | 72% | 29 |
| October 12 | +4.35% | 64% | 28 |
Best Day to Invest in COST, Month by Month
The single strongest calendar date within each month. Prefer the broader view? See the best month to invest in COST→
| Best Date | Avg Return (≈ 1 month) | Win Rate | Samples |
|---|---|---|---|
| January 15 | +3.70% | 80% | 25 |
| February 17 | +3.04% | 52% | 23 |
| March 14 | +3.33% | 61% | 28 |
| April 30 | +3.01% | 71% | 28 |
| May 25 | +5.03% | 73% | 22 |
| June 8 | +3.85% | 72% | 29 |
| July 29 | +1.73% | 59% | 29 |
| August 5 | +2.27% | 62% | 29 |
| September 21 | +3.93% | 64% | 28 |
| October 8 | +5.59% | 82% | 28 |
| November 1 | +4.81% | 71% | 28 |
| December 19 | +3.07% | 69% | 29 |
10 Weakest Days to Invest in COST
| Date | Avg Return (≈ 1 month) | Win Rate | Samples |
|---|---|---|---|
| March 30Worst | -2.85% | 43% | 28 |
| April 6 | -2.35% | 37% | 27 |
| September 4 | -2.15% | 39% | 23 |
| September 5 | -1.96% | 30% | 23 |
| April 7 | -1.71% | 43% | 28 |
| April 26 | -1.68% | 57% | 28 |
| March 23 | -1.52% | 45% | 29 |
| November 25 | -1.52% | 38% | 24 |
| July 9 | -1.44% | 57% | 28 |
| April 5 | -1.43% | 41% | 27 |
From a Single Date to a Full Seasonal Window
This page fixes the holding period at ≈ 1 month. Seasonal Edge finds the optimal entry and exit dates for each seasonal window inside the app:
- ●Optimised entry/exit dates — not just a fixed one-month hold
- ●Win rate, drawdown & equity curve for every seasonal window
- ●Cycle detection — spectral analysis projects rising and declining phases forward
How to Read This Data
Avg Return is the mean percentage change over the 21 trading days (≈ 1 month) following each calendar date, averaged across the years COST was traded.
Win Rate shows how often that forward month finished positive. A 75% win rate means COSTrose over the following month in 3 of every 4 years you invested on that date.
Samples is the number of years that contributed to the date. Calendar dates that fall on weekends or holidays in some years naturally have fewer samples; only dates with enough history are ranked.
Seasonal patterns are historical tendencies, not guarantees. A specific calendar date is a rough proxy for a seasonal window — treat it as one input alongside your own research, not a precise timing signal.
See the Full Seasonal Analysis
Seasonal Edge screens thousands of securities for seasonal patterns with daily precision — exact entry and exit dates, win rates, and historical backtests.
Try Seasonal Edge FreeFrequently Asked Questions
What is the best day of the year to invest in COST?▾
Based on 41 years of data, October 8 has historically been the best day to invest in COST. Buying on that date and holding for ≈ 1 month returned an average of +5.59% with a 82% win rate.
Does buying on one specific day really matter?▾
A single calendar date is a proxy for a seasonal window rather than a precise signal. The dates that rank highest tend to cluster around genuinely strong seasonal periods, which is why we also show the best day within each month and link through to the broader best month analysis.
How is this calculated?▾
For each calendar date we measure the return over the following 21 trading days (≈ 1 month) if you had bought on that date, using daily closing prices from 1986 to 2026, then average across all years. The date with the highest average forward return is the historically best day to invest.
Is this trading or investment advice?▾
No. This page is historical statistical analysis for educational and informational purposes only. It is not financial, investment, or trading advice and is not a recommendation to buy, sell, or hold COSTor any other security. Past performance does not guarantee future results — always do your own research and consult a qualified financial advisor before investing.