I was thinking the music star, Tommy Lee but regardless I think he is just referencing the tax return date.  Anytime sellers share a common point of failure or reason to sell, we can expect weakness like too much water in the sand the ground becomes liquid :p    Even while buyers exist the supply is greater I guess so price becomes uncertain and sold, crowd tends to follow the most obvious trend and go to the nearest support levels like a railing in the dark.   17th could well be a new day however I think globally we have many trends in play