Ever noticed how your trading week performs differently depending on the day? Looking at cumulative market gains this century broken down by day of the week reveals some fascinating patterns. Tuesday absolutely dominates with 106.64% in total gains—a massive outlier compared to the rest of the week. Wednesday follows at 45.57%, while Thursday trails slightly behind at 40.72%. Monday manages a respectable 8.99%, yet Friday barely moves the needle at 1.80%. The stark contrast between Tuesday's explosive performance and Friday's sluggish returns (excluding dividends) is striking. This historical data suggests serious day-of-the-week effects in market behavior—something worth monitoring if you're timing your trades or analyzing cyclical opportunities throughout your trading week.