“Negative Presidents’ Day
Presidents’ Day is the lone holiday that exhibits weakness the day before and after. Trading has turned more negative over the last twenty-two years. The Friday before this mid-winter three-day break is exceptionally bad, whereas the Tuesday after is not as brutal and has shown some improvement recently although average losses are greater. See Table 5.”
https://www.fidelity.com/learning-center/trading-investing/technical-analysis/holiday-trading