disable past dates on datepicker

Question

How to disable past dates from the current date on a datetimepicker? I tried few posts for similar question but was unable to achieve it, Below is what I tried

Answer 1

Set an end date based on start date using datepicker

  $("#AddEvent_txtStartDate").datepicker({
        onSelect: function () {
            minDate = $("#AddEvent_txtStartDate").datepicker("getDate");
            var mDate = new Date(minDate.setDate(minDate.getDate()));
            $("#AddEvent_txtEndDate").datepicker("setDate", mDate);
            $("#AddEvent_txtEndDate").datepicker("option", "minDate", mDate);
        }
    });  
    $("#AddEvent_txtEndDate").datepicker();