Tick Label Formatting

The default label format can be overridden by passing a function to the .tickFormat( ) method. The function is passed the numeric value of each label (which in the case of dates is the number of milliseconds since midnight on January 1, 1970).

var dateRange = ["06/30/2015", "08/31/2016"];

var bottom = new d3plus.AxisBottom()
  .tickFormat(function(ms) {
    return new Date(ms).getFullYear();