According to the annual Best Days/Worst Days study released by NAAIM member Will Hepburn of Hepburn Capital, it is likely that if you missed the best day of the market, you missed the worst day too.
Summary: The risk of selling and moving out of the stock market often focuses on missing good days and hurting overall returns. However, investors have an equal chance of missing a bad day and increasing returns. Since the best days often follow the worst days, back to back, it is statistically more likely that if an investor missed one he will miss the other. This expanded study looks at the outcome of missing both the best and worst days.
See the the full study results here: Best and Worst Days 2015