$(function() {
  var $dp1 = $("#datepicker1");
  $dp1.datepicker({
    changeYear: true,
    changeMonth: true,
      minDate:0,
    dateFormat: "yy-m-dd",
    yearRange: "-100:+20",
  });

  var $dp2 = $("#datepicker2");
  $dp2.datepicker({
    changeYear: true,
    changeMonth: true,
    yearRange: "-100:+20",
    dateFormat: "yy-m-dd",
  });
});

$dp1.datepicker({
        changeYear: true,
        changeMonth: true,
        dateFormat: "yy-m-dd",
        yearRange: "-100:+20",
        minDate: '0'
    });

javascript

$(document).ready(function() {
    $('#Date').datepicker({
        onSelect: function(dateText, inst) {

            var today = new Date();
            today = Date.parse(today.getMonth()+1+'/'+today.getDate()+'/'+today.getFullYear());

            var selDate = Date.parse(dateText);

            if(selDate < today) {

                $('#Date').val('');
                $(inst).datepicker('show');
            }
        }
    });
});

<input type="text" id="Date" value="" />

<p class="pfield-wrapper required-field"> <label>Start Date</label>         <input id="datepicker1" type="text" name="s"  style="width:155px;" required value=""></p>
    <p class="p">End Date<input id="datepicker2" type="text" name="e"  style="width:155px;" value=""></p>

$(function () {
   var $dp1 = $("#datepicker1");
  $(document).ready(function () {

  $dp1.datepicker({
    changeYear: true,
    changeMonth: true,
        minDate: '0',
    dateFormat: "yy-m-dd",
    yearRange: "-100:+20",
  });
 });

        });

          $(function () {
   var $dp2 = $("#datepicker2");


  $dp2.datepicker({
    changeYear: true,
    changeMonth: true,
       minDate: '0',
    yearRange: "-100:+20",
    dateFormat: "yy-m-dd",

 });

        });

<p class="pfield-wrapper required-field"> <label>Start Date</label>         <input id="datepicker1" type="text" name="s"  style="width:155px;" required value=""></p>
    <p class="p">End Date<input id="datepicker2" type="text" name="e"  style="width:155px;" value=""></p>

$('#datepicker1').datepicker({
        onSelect: function(dateText, inst) {
            //Get today's date at midnight
            var today = new Date();
            today = Date.parse(today.getMonth()+1+'/'+today.getDate()+'/'+today.getFullYear());
            //Get the selected date (also at midnight)
            var selDate = Date.parse(dateText);

            if(selDate < today) {
                //If the selected date was before today, continue to show the datepicker
                $('#datepicker1').val('');
                $(inst).datepicker('show');
            }
        }
    });



$('#datepicker2').datepicker({
        onSelect: function(dateText, inst) {
            //Get today's date at midnight
            var today = new Date();
            today = Date.parse(today.getMonth()+1+'/'+today.getDate()+'/'+today.getFullYear());
            //Get the selected date (also at midnight)
            var selDate = Date.parse(dateText);

            if(selDate < today) {
                //If the selected date was before today, continue to show the datepicker
                $('#datepicker2').val('');
                $(inst).datepicker('show');
            }
        }
    });

$(document).ready(function(){
$("#txtFromDate").datepicker({
     minDate: '0',
    onSelect: function(selected) {
      $("#txtToDate").datepicker("option","minDate", selected)
    }
});
$("#txtToDate").datepicker({
     minDate: '0',
    onSelect: function(selected) {
       $("#txtFromDate").datepicker("option","maxDate", selected)
    }
});
});