We can see that the 1st DEATH CROSS occured late 2013 and was the start of a 550 day bear market. A death cross is when the 50SMA (pink) crosses beneath the 200SMA ( blue).
After 550 days the market recovered and started an uptrend. But after 1200 days the previous all time high was reached.
At the moment a 2nd death cross is almost on its way, we will have to see if history repeats.....