date( ) returns 1970-01-01

I am using a jquery datepicker with the following format mm/dd/yyyy but I need it to be yyyy-mm-dd for the sql db so I am using this.

   $date  = date("Y-m-d",strtotime($startdate));

with the following

 $query = "INSERT INTO complete_table ( name, startdate) VALUES ('$_POST[name]', '$date')";

Unfortunately I register 1970-01-01 in the db regardless of what the input is. Any idea on what I am doing wrong? Thank you so much for the help.