$(document).ready(function(){

  $('.date_picker').datetimepicker({
      pickTime: false
  });

  $('.default_picker').datetimepicker();

  $('.time_picker').datetimepicker({
      pickDate: false
  });

  $('.separated_picker div').on("changeDate",function(){
    $(this).siblings('input').val($(this).find('input').val() + ' ' + $(this).siblings('div').find('input').val());
  });

});