<input type="text" id="edit-date" placeholder="Pick date...">

<div>

  <button data-date="2019-01-01" data-value="[2019,0,1]">Set Datepicker to 2019-01-01</button>

  <button data-date="2019-12-31" data-value="[2019,11,31]">Set Datepicker to 2019-12-31</button>

</div>

​

$('#edit-date').pickadate("update", new Date("01/10/2014"));

$("#edit-date").pickadate();

$("button").click(function(){

  var date = $(this).data("date");

  var value = $(this).data("value");

  $("#edit-date").val(date);

  $("#edit-date").data("value", value);

})