This is the comparison of 2013-15 and 2017-19 only based on the date-price(percentage) data. If BTC follows the same pattern as it followed in 2013-15, the bear market will last until mid-Sep 2019.
Not sure if this one is true because the popularity of Bitcoin in 2013-15 is nothing comparing to today. That is why I think the bear market was so long in 2013.