Worst day in more than six years

What compounds the drop is that it came after a tough day on Friday. Given the high levels of the main indexes, the numerical drops also look particularly daunting -- like the 1176 drop in the Dow Jones Industrial Average.

On August 8, the S&P 500 fell 6.6%.

There are a lot of similarities to that day. First, it came on a Monday after a few tough days in the week prior.

Second, there wasn't a big catalyst. The news was relatively good before and afterwards.

What happened next?

The market fell a bit further on Tuesday at the open but it ended up bouncing 4.6% and closed at the highs. The selling returned Wednesday but the lows held.

After another rout two months later, the market eventually got back on its feet and climbed to new highs. Of course, it took five months.